Strigolactones as Integrative Regulators of Plant Adaptation and Resilience to Abiotic Stress

ABSTRACT

Climate change represents a major global challenge, intensifying abiotic stresses such as drought, salinity and temperature extremes, that severely constrain productivity and threaten food security. To survive under such fluctuating and adverse environments, plants depend on intricate hormonal signalling networks that coordinate growth regulation, resource allocation and stress adaptation. Among these, strigolactones (SLs) have emerged as integrative regulators that bridge developmental control with environmental responsiveness, thereby enhancing plant resilience to climate‐induced stresses. Initially discovered as rhizospheric signals influencing parasitic weed germination and symbiotic associations, SLs are now recognized as multifunctional phytohormones regulating shoot branching, root system architecture, senescence and reproductive growth. SLs encounter in extensive crosstalk with other hormones notably abscisic acid, auxins and cytokinins to modulate physiological and molecular responses under stress. This review consolidates recent advances in understanding the role of SLs as central mediators of plant adaptation to climate‐induced abiotic stresses, emphasizing their integrative signalling roles and interactions with other phytohormones. It also explores emerging molecular, genetic and biotechnological strategies targeting SL pathways for enhancing stress resilience. Unravelling the complex SL signalling network delivers key conceptual inputs for providing climate‐smart crops capable of sustaining productivity and stability under the increasing pressures of global climate change.

Summary statement

Strigolactones function as central modulators of plant hormonal and stress signalling networks, orchestrating growth, developmental processes and adaptive responses under abiotic stress. Their biosynthesis and perception pathways interact with other phytohormones, integrating transcriptional, physiological and morphological mechanisms that underpin stress tolerance and adaptation.

1. Introduction

Ensuring global food security has become one of the foremost priorities for plant scientists in the 21st century. The escalating effects of climate change, coupled with rapid population growth, are exerting unprecedented pressure on agricultural systems and natural ecosystems alike (Kusajima et al. 2025). Climate variability, characterized by rising temperatures, recurrent droughts, salinity intrusion and erratic precipitation patterns, severely impacts plant productivity and survival. Due to their sessile nature, as opposed to the mobility seen in other organisms, plants must cope with ever‐changing environmental factors, requiring them to develop intricate adaptive strategies to ensure growth and reproduction. These persistent stresses disrupt cellular structures, impair photosynthesis and interfere with vital metabolic and signalling pathways, collectively threatening global food production and ecosystem stability.

Abiotic stresses such as moisture deficit, saline soils, unfavourable temperatures and nutritional limitations are now recognized as major constraints to agricultural productivity (Wang et al. 2025). These stresses alter nutrient uptake, metabolism and biosynthetic capacity, leading to physiological imbalances and reduced yield potential. Environmental stress also affects cellular signalling and gene expression by activating specific transcription factors and stress‐responsive pathways that reprogramme metabolism to support tolerance mechanisms (Zhu 2016) Over the life cycle of a plant, these environmental challenges often acting in combination can lead to crop failure, biodiversity loss and a decline in ecosystem services (Abdelrahman et al. 2018). Experimental studies have shown that water stress significantly reduces photosynthesis and transpiration, while elevated temperatures further exacerbate these effects, impairing carbon assimilation and water‐use efficiency (Zhang et al. 2020; Zhao et al. 2024). To survive such harsh conditions, plants have developed complex networks of morpho‐physiological, biochemical and molecular responses coordinated through signal transduction and genetic reprogramming (Song et al. 2024). Central to these adaptive mechanisms are phytohormones, which serve as critical signalling molecules regulating growth, metabolism and stress responses. Among them, strigolactones (SLs) have recently gained attention as potent regulators that bridge developmental and stress‐related processes (Ali et al. 2025; Hu et al. 2025; Kusajima et al. 2025). These carotenoid‐derived terpenoid lactones have emerged as integrative hormonal players that modulate plant adaptation to both internal and external cues.

In addition to classical stress‐related hormones, for instance, abscisic acid (ABA), jasmonates (JA), ethylene and cytokinins (CKs), SLs are now identified for their distinctive function in modulating oxidative balance and enhancing plant resilience (Wang et al. 2025). Oxygen, while essential for life, can also act as a double‐edged sword in plant metabolism. During photosynthesis and respiration, reactive oxygen species (ROS) such as superoxide radicals, hydroxyl radicals and hydrogen peroxide are continuously generated in chloroplasts, mitochondria and peroxisomes. Under optimal conditions, ROS serve important roles as signalling molecules, mediating growth, development and defence. However, under stress, excessive ROS accumulation leads to oxidative injury of lipids, proteins, nucleic acids and membranes, finally resulting in cell death. Thus, maintaining a delicate equilibrium between ROS and scavenging through antioxidant defence systems is crucial for plant survival and productivity (Kusajima et al. 2025).

Recent findings have revealed that SLs function as critical contributors to reinforcing plant oxidative defence under various stress conditions. These hormones contribute to stress mitigation by modulating antioxidants activity, reducing ROS and stabilizing membrane integrity. SLs have been shown to suppress oxidative damage by regulating key enzymes such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), thereby protecting chloroplasts and maintaining photosynthetic efficiency (Ma et al. 2017). Experiments using SL‐deficient mutants and exogenous SL treatments have demonstrated enhanced tolerance to salinity through improved ROS scavenging and osmotic regulation (Sharifi and Bidabadi 2020). Likewise, SLs contribute to resilience under low‐light, drought, heat and cold stress, by activating antioxidant responses, sustaining water balance and preserving photosynthetic apparatus functionality (Ali et al. 2025; Min et al. 2019; Hu et al. 2025; Ling et al. 2020; Kusajima et al. 2025; Sedaghat et al. 2021). Beyond oxidative defence, SLs exert a broad influence on root–shoot communication and symbiotic interactions. They serve as chemical signals promoting arbuscular mycorrhizal fungi (AMF) colonization by stimulating hyphal branching, which enhances nutrient and water acquisition, an adaptive advantage under nutrient‐deficient or drought conditions (Yoneyama 2019; Sedaghat et al. 2017). Moreover, their crosstalk with ABA signalling is critical for regulating stomatal behaviour and improving salt tolerance, reflecting their integrative role in hormonal networks coordinating stress adaptation. Collectively, these findings position strigolactones as key orchestrators in plant oxidative and stress defence systems, mediating both physiological and molecular adaptations to environmental adversity. Their multifaceted functions ranging from developmental regulation to stress signalling highlight the potential of SLs as targets for biotechnological and breeding interventions aimed at enhancing crop resilience. Understanding the intricate mechanisms of SL action under climate‐induced stresses is essential for developing climate‐smart agriculture strategies and supporting long‐term agricultural productivity amid accelerating environmental shifts worldwide.

2. Biosynthesis of Strigolactones (SLs)

SLs are a unique series of carotenoid‐derived terpenoid lactones that function as multifunctional phytohormones and rhizospheric signalling compounds. Structurally, SLs possess a conserved four‐ring system, consisting of an ABC tricyclic lactone core connected through an enol ether bridge to an α,β‐unsaturated butenolide D‐ring a moiety essential for their biological activity. The A–B rings exhibit structural diversity in carbon number, double‐bond configuration and substituent groups, while the C‐ and D‐rings remain relatively conserved. On the basis of the stereochemistry of the B–C junction, SLs are classified into two major classes: strigol‐type (β‐oriented C‐ring) and orobanchol‐type (α‐oriented C‐ring) (Mashiguchi et al. 2021). To date, over 20 naturally occurring SLs and SL‐like molecules have been isolated from diverse land plants, revealing significant structural and functional diversity. The bioactive centre (bioactiphore) lies within the enol‐ether bridge linking the D‐ring to the centre structure, which varies slightly among SL types and dictates their biological specificity. Beyond their endogenous hormonal roles, SLs play vital ecological functions mediating rhizosphere communication, promoting symbiosis with arbuscular mycorrhizal fungi, and activating the germination process of parasitic plants, including Striga and Orobanche.

2.1. Core Biosynthetic Pathway and Key Enzymes

The biosynthesis of SLs begins in plastids and proceeds through a sequence of isomerization, cleavage, oxidation and cyclization reactions catalysed by enzymes encoded by conserved gene families such as D27, CCD7, CCD8 and MAX1. The process initiates with the isomerization of all‐trans‐β‐carotene to 9‐cis‐β‐carotene by the carotenoid isomerase DWARF27 (D27). Subsequently, carotenoid cleavage dioxygenase 7 (CCD7) cleaves 9‐cis‐β‐carotene to yield 9‐cis‐β‐apo‐10′‐carotenal, which is then transformed by CCD8 into carlactone (CL), the universal precursor of SLs (Han et al. 2025).

CL represents a pivotal step in SL formation, as it completes the assembly of the characteristic D‐ring and establishes the fundamental molecular scaffold required for subsequent structural diversification. This key intermediate is generated within plastids and subsequently transported to the cytosol, where it undergoes further oxidative tailoring. In this compartment, cytochrome P450 monooxygenases belonging to the CYP711A family, commonly referred to as MAX1 enzymes, catalyse a series of oxidation reactions that convert CL into carlactonoic acid (CLA) and additional SL‐related metabolites. In Arabidopsis, which harbours a single MAX1 homologue, CL is oxidized to CLA, followed by methylation mediated by a specific methyltransferase, carlactonoate methyltransferase (CLAMT), yielding methyl carlactonoate (MeCLA). This compound functions as a bioactive intermediate that participates in downstream SL signalling processes (Abe et al. 2014). Subsequently, the lateral branching oxidoreductase enzyme hydroxylates MeCLA to produce hydroxymethyl carlactonoate, thereby fine‐tuning SL bioactivity and contributing to the formation of non‐canonical SL variants (Brewer et al. 2016). This step highlights the importance of post‐methylation modifications in modulating SL function and signalling specificity.

Recent investigations in maize have revealed the existence of an alternative and previously uncharacterized branch of SL biosynthesis. In this pathway, the cytochrome P450 enzyme ZmCYP706C37 operates in conjunction with the maize MAX1 homologue and CLAMT to convert CL into zealactone via two distinct biochemical routes (Li et al. 2023). This discovery highlights the evolutionary diversification of SL biosynthesis across plant species. A comparable mechanism has been identified in rice, where the homologous enzyme OsCYP706C2 collaborates with the MAX1 homologue Os900 and 4‐OXO‐CLA METHYL TRANSFERASE (Os4OCLAMT) to channel CL into the production of the non‐canonical strigolactone 4‐oxo‐methyl carlactonoate (4‐oxo‐MeCLA) (Li et al. 2024). These findings further underscore the metabolic plasticity of SL biosynthesis and the existence of species‐specific biosynthetic routes. In addition to these pathways, certain plant species generate orobanchol‐type SLs directly from CLA. For instance, in tomato, the cytochrome P450 enzyme CYP722C catalyses the closure of the BC‐ring, thereby converting CLA into orobanchol. Subsequently, SlCYP712G1 mediates the oxidation of orobanchol to form didehydro‐orobanchol, a key intermediate in the biosynthesis of solanacol (Wang et al. 2022). Collectively, these studies illustrate the remarkable biochemical diversity of SL biosynthesis and the central role of P450 enzymes in shaping species‐specific SL profiles.

2.2. Species Diversification of SL Biosynthesis

Although the core biosynthetic route up to CL is evolutionarily conserved, downstream modifications differ significantly among plant taxa, resulting in distinct SL profiles (Figure 1). In rice (Oryza sativa), a set of five homologous sequences of MAX1 are included among these, Os900 (CYP711A2) and Os1400 (CYP711A3) sequentially convert CL into CLA, and subsequently into 4‐deoxyorobanchol (4DO) and orobanchol, respectively (Yoneyama et al. 2018). In contrast, in Vigna unguiculata and Solanum lycopersicum, the CYP722C enzyme immediately transforms CLA into orobanchol, bypassing the 4DO transitional (Wakabayashi et al. 2019). Similarly, in cotton (Gossypium hirsutum), CYP722C catalyses the formation of 5‐deoxystrigol (5DS), the simplest canonical SL and a presumed evolutionary precursor for more complex SLs (Wakabayashi et al. 2020). Other P450 enzymes, such as CYP728B35, further modify 5DS to yield sorgomol, expanding the structural diversity of SLs. Thus, at least three major P450 clades, CYP711A, CYP722C and CYP728B, are now known to contribute to SL diversification across species. This enzymatic heterogeneity underscores the adaptive evolution of SL biosynthesis, allowing plants to modulate rhizospheric signalling and stress responses under varying ecological and nutrient conditions.

Figure 1.

Structural, biosynthetic, and functional overview of strigolactones (SLs) in plants. (A) Representative chemical structures of carlactone (CL), a biosynthetic precursor of strigolactones, and strigol, a canonical strigolactone. Strigol exhibits the characteristic tricyclic lactone (ABC rings) linked to a methylbutenolide (D ring) via a conserved enol‐ether bridge, whereas CL lacks the complete ABC scaffold and represents an early intermediate in the strigolactone biosynthetic pathway. (B) SL biosynthesis is initiated in plastids, where all‐trans‐β‐carotene is converted to carlactone (CL) through the sequential action of DWARF27 (D27), carotenoid cleavage dioxygenase 7 (CCD7), and CCD8. CL is converted in the cytoplasm into carlactonoic acid (CLA) by MAX1 (CYP711A family). Depending on the species, CLA is then converted into different SL types; while enzymes like CYP722C lead to the production of orobanchol (a canonical SL), the action of methyltransferases followed by LBO leads to the formation of 1'‐OH‐MeCLA, a proposed bioactive non‐canonical SL. This pathway is species‐dependent and observed in certain plant species, producing diverse canonical and non‐canonical SLs. Phosphate deficiency can upregulate SL biosynthesis in certain plant species. (C) SLs are transported via the xylem and actively secreted into the rhizosphere by the ABC transporter PDR1 (species‐dependent). Functionally, SLs regulate shoot branching, modulate root system architecture, promote symbiosis with arbuscular mycorrhizal fungi, induce germination of parasitic plant seeds, and contribute to plant adaptation to stresses.

2.3. Regulation of SL Biosynthesis and Environmental Cues

SL biosynthesis is a highly plastic and environmentally responsive process, reflecting the integrative role of these hormones in coordinating plant development with external cues. Nutrient availability is a major regulatory determinant of SL production, with phosphate (Pi) deprivation representing one of the strongest inducers. Under Pi‐limiting conditions, the transcription of core SL biosynthetic genes, including D27, CCD7, CCD8 and MAX1, is markedly upregulated, thereby enhancing SL accumulation and promoting adaptive responses such as altered root architecture and the establishment of symbiotic interactions with arbuscular mycorrhizal fungi to improve nutrient acquisition (Shi and Yu 2025). In addition to phosphate scarcity, other environmental stresses such as nitrogen limitation, drought and salinity have also been reported to stimulate SL biosynthesis, linking SL signalling to broader stress‐response and resource‐allocation networks.

Homeostatic regulation of SL levels is further achieved through feedback control mechanisms. In several plant species, mutants defective in SL biosynthesis or perception (max, rms, dad and dwarf mutants) frequently exhibit elevated expression of SL biosynthetic genes, indicative of negative feedback loops that act to stabilize endogenous SL pools. This multilayered regulatory architecture ensures tight control over SL abundance and signalling competence. Beyond biosynthesis and perception, emerging evidence highlights the importance of SL transport in shaping hormone function. In petunia, the ATP‐binding cassette (ABC) transporter PhPDR1 has been shown to mediate SL export from roots into the rhizosphere, thereby influencing long‐distance signalling and root–microbe communication (Sasse et al. 2015). This discovery provided the first direct indication that SL action is governed not only by synthesis and reception but also by controlled cellular and inter‐organ distribution.

More recent studies have identified additional SL efflux transporters, significantly expanding the conceptual framework of SL biology. These findings demonstrate that SL signalling outcomes depend on the precise spatial and temporal regulation of hormone flux, rather than on biosynthesis alone. In Sorghum bicolor, two ABCG transporter homologues, SbSLT1 and SbSLT2, have been characterized as plasma membrane–localized SL exporters. These transporters facilitate the secretion of SLs into the rhizosphere, particularly under phosphate‐deficient conditions, when SL exudation is strongly enhanced (Shi and Yu 2025). Loss‐of‐function mutants of these transporters exhibit substantially reduced SL release from roots, which in turn suppresses the germination of parasitic Striga seeds. Notably, this reduction in parasitic stimulation occurs without major penalties to plant growth, highlighting the potential of SL transporter manipulation as a targeted strategy for improving resistance to parasitic weeds (Shi and Yu 2025).

A comparable regulatory system has been reported in tomato (Solanum lycopersicum), where the ABCG family members SlABCG45 and SlABCG44 function as bona fide SL transporters. These proteins are predominantly expressed in the root epidermis and appear to perform dual roles: mediating SL exudation into the surrounding soil and facilitating their acropetal transport from roots to shoots (Ban et al. 2025). Targeted genome editing of SlABCG45 confers enhanced resistance to parasitic plants such as Phelipanche and Orobanche while maintaining key agronomic traits, including yield stability. This result demonstrates that selective modulation of SL transport can decouple the hormone's rhizospheric signalling functions from its endogenous developmental roles. The emerging importance of transporter‐mediated SL distribution plays an important role as an integral component of the SL regulatory network. Incorporating SL transport into the conceptual model of SL action provides a more holistic understanding of how these hormones orchestrate plant–environment interactions, coordinate nutrient stress responses and shape rhizospheric communication. From an applied perspective, this transport‐centred view opens new opportunities for sustainable crop protection strategies that rely on altering SL flux rather than directly manipulating biosynthesis, thereby minimizing pleiotropic effects on plant architecture.

2.4. Synthetic Strigolactones and Functional Applications

Because natural SL concentrations in plants are extremely low (typically 15–30 pg per plant per day) and prone to instability, chemically synthesized analogues and mimics have been created to explore SL signalling and exploit their agricultural potential. Among these, GR24 and its derivatives remain widely adopted synthetic analogues, recognized for their chemical resilience and strong biological function (Figure 2). Synthetic SLs are classified as analogues (structurally similar to natural SLs) or mimics (functionally similar but structurally distinct). Compounds such as GR24, MP16–MP25, CISA‐1 and AR36 have been employed to investigate SL functions in shoot branching regulation, leaf senescence, parasitic weed management and drought tolerance improvement (Chesterfield et al. 2020). Beyond their role in developmental control, synthetic SLs offer promising applications for enhancing crop resilience under climate‐induced stresses by modulating root architecture, reducing tillering under nutrient stress and improving symbiotic efficiency with arbuscular mycorrhizal fungi.

Figure 2.

Strigolactones (SLs) and structurally related compounds.

2.5. Integrative Perspective

MAX1 enzyme family and associated cytochrome P450s represent the central catalytic machinery governing SL diversification and function. The evolution of multiple enzyme homologues and downstream modifications across plant species underscores the adaptive flexibility of the SL pathway, enabling plants to fine‐tune their growth, architecture and stress responses under fluctuating environmental conditions. Understanding these biosynthetic and regulatory complexities provides an essential foundation for developing strigolactone‐based biotechnological approaches to improve crop tolerance to nutrient deficiency, drought and other climate‐induced stresses (Chesterfield et al. 2020).

3. Roles of Strigolactones in Abiotic Stresses

Plants are continuously exposed to dynamic environmental challenges, many of which are intensifying due to global climate change. These stressors including drought, salinity, extreme temperature fluctuations, heavy metal toxicity and nutrient depletion severely constrain crop productivity and threaten global food security. In response, plants deploy intricate hormonal signalling networks to reprogramme their growth and metabolism, among which SLs play a pivotal role. Figure 3 provides a concise, integrative overview of the strigolactone signalling network under abiotic stress. It illustrates SL biosynthesis, perception via D14/MAX2, downstream degradation of SMXL proteins and activation of transcription factors (DREB1, WRKY41) leading to stress‐adaptive responses such as stomatal closure, ROS detoxification, osmotic adjustment and root remodelling (Chi et al. 2021). Under stress conditions, SL biosynthesis and signalling are typically upregulated, enabling plants to modify developmental strategies and optimize resource use for improved survival and resilience. Although early investigations primarily focused on arid and semi‐arid ecosystems, the implications of SL‐mediated stress tolerance extend far beyond these regions, particularly as climate change increases the incidence and intensity of abiotic stress events worldwide. Shifts in temperature regimes, prolonged droughts and irregular precipitation patterns disrupt soil biogeochemical cycles, diminish nutrient availability and alter plant community composition (Khedr et al. 2023). These perturbations directly affect nitrogen and phosphorus dynamics in plant–soil systems, as field studies have shown that water scarcity markedly reduces the mobility and uptake of these essential nutrients. Consequently, there is an urgent need to develop innovative physiological and biotechnological solutions that enhance plant adaptation to such multifactorial stress conditions.

Figure 3.

Schematic representation of the strigolactone (SL) signaling network involved in stress responses and adaptation. SL biosynthesis regulation under stress is highly stress‐specific, with distinct biosynthetic targets affected by different stresses. Downstream responses and stress adaptation are influenced by stress type, plant species, and physiological context. [Color figure can be viewed at wileyonlinelibrary.com]

SLs have emerged as versatile hormonal regulators that enable plants to maintain growth under stress. By modulating root patterning and structure, SLs enhance the plant's ability to explore soil layers for water and nutrients, while simultaneously restricting excessive shoot branching to reduce transpirational water loss. This adaptive reconfiguration is especially valuable under drought and nutrient‐limited conditions. Moreover, SLs promote AMF symbiosis, thereby facilitating P and micronutrient acquisition from impoverished soils, a process that is especially critical under global nutrient‐depletion scenarios (Gao et al. 2022). Salinity, another escalating challenge under climate change, severely disrupts ionic homeostasis and metabolic processes in plants. Emerging evidence suggests that SLs contribute to salt tolerance by enhancing antioxidant defence systems, regulating Na⁺/K⁺ balance, and maintaining photosynthetic efficiency (Ullah et al. 2022; Khedr and Khedr 2024). Genetic evidence indicates that endogenous SL contributes to seed germination and early seedling establishment under adverse conditions. In parallel, exogenous application of synthetic SL analogues, such as GR24, has been shown to enhance seed germination, root elongation and early seedling vigour under osmotic and thermal stress (Zhang et al. 2020).

Beyond their roles in agricultural systems, SLs may also hold potential for ecosystem restoration under climate stress. Many native plant species that act as ecological stabilizers such as Alhagi sparsifolia, a key species combating desertification in Central and Eastern Asia face severe germination and survival challenges due to rising temperatures, prolonged droughts and nutrient depletion (Gao et al. 2022). Strengthening SL signalling or applying SL‐based treatments could enhance the establishment and resilience of such species, contributing to ecosystem recovery and land rehabilitation. Given that phosphorus is one of the most limiting nutrients in degraded soils, the ability of SLs to stimulate both root hair development and mycorrhizal associations provides a promising strategy for improving nutrient uptake efficiency. Applying SL analogues such as GR24 to seeds or seedlings before transplantation in nutrient‐poor soils may significantly improve early root growth and water acquisition before drought onset. Furthermore, optimizing SL use in major crops could enhance nutrient use efficiency, yield stability and stress resilience, supporting sustainability in the face of ongoing climate change. In light of these findings, further research into the diversity and function of naturally exuded SLs from plants thriving in nutrient‐poor and climate‐stressed environments is warranted. Identifying novel SL variants or signalling mechanisms from such species could provide valuable insights for developing next‐generation biostimulants aimed at enhancing crop yields while strengthening ecosystem stability under accelerating climate change.

3.1. Strigolactones During Heat Stress

Heat stress represents a major pervasive and damaging consequences of climate change, severely limiting plant productivity, physiology and survival. Elevated temperatures impair photosynthesis, disrupt cellular homeostasis and accelerate water loss, collectively reducing growth and yield. Among the diverse mechanisms plants deploy to mitigate such stress, SLs have emerged as key hormonal mediators that coordinate developmental and metabolic responses to thermal extremes (Figure 4). On the molecular basis, SLs regulate the expression of heat‐responsive and antioxidant‐related genes, thereby mitigating oxidative stress caused by elevated temperatures. In Solanum lycopersicum, SLs have been reported to upregulate the transcription of genes encoding key antioxidant enzymes, including SOD, ascorbate peroxidase (APX), glutathione reductase (GR) and dehydroascorbate reductase (DHAR) thereby strengthening ROS‐scavenging capacity (Chi et al. 2021). In addition, SLs upregulate genes for heat shock proteins (HSPs), which function as molecular chaperones preserving protein stability and preventing aggregation under high temperatures (Khan and Shahwar 2020). These protective functions are supported by the observation that key SL biosynthetic and signalling genes including CCD7, CCD8, MAX1 and MAX2 are induced when exposed to high and low temperature stresses, reinforcing the hypothesis that SL pathways act as broad‐spectrum modulators of thermal resilience (Chi et al. 2021). Table 1 presents different examples of the effects of strigolactones on plant physiological and molecular responses under temperature fluctuation stress.

Figure 4.

A proposed schematic model of strigolactone‐mediated responses to heat stress in plants. [Color figure can be viewed at wileyonlinelibrary.com]

Table 1.

Effects of strigolactones on plant physiological and molecular responses under temperature fluctuation stress.

Plant species	Effects of SLs	References
Mung bean (Vigna radiata)	SL treatment improves plant water status and stress tolerance by increasing relative water content (RWC), antioxidant enzyme activities (SOD) and phenylpropanoid‐related enzymes (PAL, TAL, LOX), as well as total soluble sugars and proline. Concurrently, SLs reduce oxidative damage by decreasing O₂•⁻, H₂O₂, phenolics and malondialdehyde (MDA) contents.	Omoarelojie et al. (2021)
Tomato (Solanum lycopersicum)	SLs enhance cold tolerance by elevating the activities of antioxidant enzymes (SOD, APX, GR, MDAR and DHAR), increasing endogenous ABA levels, and upregulating the expression of stress‐related genes such as NCED6, HSP70 and CBF1.	Chi et al. (2021)
Tomato (Solanum lycopersicum)	Treatment with the synthetic SL analogue GR245DS significantly enhances cold tolerance by promoting autophagy, as evidenced by increased autophagosome accumulation and elevated expression of autophagy‐related genes (ATGs), along with reduced accumulation of ubiquitinated proteins. Cold stress–induced accumulation of ELONGATED HYPOCOTYL 5 (HY5) is mediated by SLs, and HY5 further activates ATG18a transcription, thereby stimulating autophagy formation.	Chi et al. (2025)
Turnip rape (Brassica rapa L.)	SLs enhance antioxidant defence by increasing the activities of SOD, POD, CAT and APX, and promote stress tolerance through elevated soluble protein and proline contents. SLs also upregulate the expression of stress‐responsive genes, including SOD, POD, CAT, APX, MPK3, MPK6, ICE1 and COR.	Zhang et al. (2020)

Genetic evidence indicates that endogenous SL plays a crucial physiological role in maintaining water balance and redox homeostasis under high‐temperature stress. In tomato, SL‐deficient mutants exhibit excessive stomatal opening and accelerated water loss, highlighting the importance of intact SL biosynthesis and signalling for proper stomatal regulation (Chi et al. 2021). In parallel, exogenous application of the synthetic SL analogue GR24 has been reported to reduce stomatal conductance and enhance leaf water retention under heat stress. However, these responses should be interpreted as physiological effects that may not fully recapitulate the native physiological functions of endogenous SLs, particularly when applied at supra‐physiological concentrations. GR24 treatment has also been shown to stimulate enzymatic antioxidant systems, thereby limiting ROS accumulation and preserving chloroplast ultrastructure, which is essential for sustaining photosynthetic performance under heat stress (Khedr et al. 2025). This protective effect further extends to non‐enzymatic antioxidant mechanisms, including the accumulation of phenolic compounds and proline, which contribute to osmotic adjustment and membrane stabilization (Omoarelojie et al. 2021).

Morphologically, SLs mitigate the detrimental effects of high‐temperature stress on root and shoot development. High temperatures typically inhibit root elongation in cool‐season grasses and other thermosensitive plants. In Festuca arundinacea (tall fescue), GR24 application restored root growth under heat stress by enhancing the elongation of crown roots and increasing the number of root cells. These responses were associated with increased expression of cell‐cycle‐associated genes, including proliferating cell nuclear antigen (PCNA), cyclin‐D2 and cyclin‐dependent kinase B (CDKB), along with the regulation of auxin passage‐related genes like PIN1 and PIN2 (Hu et al. 2018). Likewise, treatment with GR24 enhanced leaf elongation under heat stress, reflecting its similarly positive influence on root growth and development (Hu et al. 2019). Such dual regulation ensures a balanced growth response that supports both nutrient acquisition and canopy expansion under thermal stress.

The regulatory interaction of SLs accompanied by phytohormones, notably ABA, cytokinin (CK) and gibberellins (GA), further enhances heat tolerance. During heat stress, an increased ABA/GA ratio inhibits seed germination and vegetative growth, contributing to thermo‐inhibition. SLs modulate this hormonal balance by promoting ABA catabolism and enhancing GA and CK levels, thereby facilitating germination and early growth even under high temperatures (Lechat et al. 2015). For instance, GR24 reversed temperature‐induced dormancy in Pasteuria seeds by activating the ABA‐catabolic gene CYP707A1, resulting in reduced ABA content and successful germination (Lechat et al. 2015). Similarly, SL‐deficient mutants of Arabidopsis thaliana (max1‐1 and max2‐1) exhibited impaired germination under heat stress, which was partially rescued by exogenous GR24, emphasizing the hormone's essential role in thermal tolerance (Tsuchiya et al. 2010).

Beyond seed and root growth, SLs have also been implicated in protecting photosynthetic machinery. In Pisum sativum and A. thaliana, SL‐deficient mutants (RMS5‐3, RMS3‐1, MAX4‐1) exhibited reduced shoot biomass and impaired chlorophyll stability under chilling and dark‐cold conditions, while GR24 treatment restored light‐harvesting gene expression and biomass accumulation (Cooper et al. 2018). This evidence supports the hypothesis that SLs function to upregulate light‐related and photosynthetic processes, enhancing plant acclimation to temperature fluctuations. In MAX2 mutants, downregulation of cytokinin oxidase/dehydrogenase (CKX) genes such as CKX1, CKX3 and CKX5 further indicates cross‐talk between SL and CK pathways in providing hormonal homeostasis during temperature stress. Taken together, the current body of research demonstrates that SLs mitigate the adverse properties of heat stress by orchestrating a multilayered protective network involving gene regulation, hormonal balance, antioxidant activation and morphological adaptation. The application of GR24 has proven effective in enhancing seed germination, root and leaf growth, and cellular protection in diverse plant species, highlighting its effect as a biostimulant for improving crop performance under rising global temperatures. Nevertheless, the molecular processes causing GR24‐arbitrated thermo‐tolerance to remain incompletely understood. Further investigations into SL–hormone cross‐talk, signal transduction, and interaction with ROS and osmoprotectant pathways will be essential to harness SL‐based strategies for climate‐smart agriculture.

3.2. Functions of Strigolactones in Plant Cold Stress Tolerance

Low temperatures are among the most detrimental abiotic factors affecting global crop productivity, often resulting in substantial yield losses and impaired plant development (Omoarelojie et al. 2021). Exposure to chilling or freezing stress disrupts photosynthetic performance, damages cellular membranes and disturbs water relations in many plant species. Interestingly, emerging evidence reveals the essential role of SLs in controlling plant responses to low‐temperature stress through complex molecular and physiological mechanisms (Figure 5). Early studies revealed that SL‐deficient mutants, such as Arabidopsis (max2‐1 and max4‐1) and Pisum (rms4), exhibit significantly reduced leaf area and photosynthetic activity under chilling stress compared to their respective wild types. These findings imply that SLs and their associated signalling genes (MAX and RMS4) contribute to the maintenance of photosynthetic efficiency and leaf development under cold conditions (Cooper et al. 2018).

Figure 5.

Strigolactone‐mediated regulation of cold stress tolerance in plants. This schematic illustrates how strigolactones (SLs) enhance plant tolerance to cold stress through molecular signaling and physiological adaptation. (A) Under cold stress, plants exhibit decreased photosynthetic efficiency (PSII), increased ROS (H₂O₂, O₂•⁻), and membrane damage, leading to oxidative injury, dehydration, and stunted growth. (B) The SL analog GR24 binds to the receptor D14, forming the D14–MAX2–SCF ubiquitin ligase complex, which degrades repressors such as SMXLs and WRKY41. This activates transcription factors ICE1 and DREB1/CBF, inducing cold‐regulated (COR) genes and those encoding antioxidant enzymes (SOD, CAT, APX, POD), as well as signaling components like Rboh (NADPH oxidase) and MAPKs (MPK3, MPK6). Anthocyanin biosynthesis genes are also upregulated. (C) SL‐mediated signaling enhances photosynthetic activity (bright chloroplasts), membrane stability, and accumulation of osmoprotectants such as proline. Strengthened antioxidant defenses lower ROS levels, while modulation of anthocyanin accumulation contributes to photoprotection. Collectively, these responses highlight the role of SLs in activating antioxidant defense, osmotic adjustment, and gene expression to confer adaptation of plants to chilling conditions. All effects are species‐, tissue‐, and context‐dependent. [Color figure can be viewed at wileyonlinelibrary.com]

In Brassica rapa, exogenous treatment of GR24 markedly improved plant performance under chilling conditions. GR24‐treated plants displayed enhanced photosynthetic activity, cell viability and accumulation of protective metabolites such as soluble proteins and proline, alongside increased antioxidant enzyme activities. Moreover, the treatment significantly lowered relative electrical conductivity, indicating reduced membrane damage. Transcript analysis further demonstrated that GR24 induces the expression of cold‐responsive and defence‐correlated genes, including antioxidant enzymes, NADPH oxidase and MAPK signalling components, thereby strengthening the plant's resilience to cold stress (Zhang et al. 2020). Similarly, in Vigna radiata (mung bean), chilling stress severely inhibited PSII efficiency and disrupted plant water balance. GR24 application mitigated these adverse effects by decreasing lipid peroxidation and stimulating the accumulation of osmoprotectants such as proline. In addition, it upregulated key enzymes in the lipoxygenase and phenylpropanoid pathways, further enhancing cellular protection against chilling injury (Omoarelojie et al. 2021).

Molecular studies have also linked SL signalling to temperature‐induced gene regulation. In Oryza sativa, low temperature suppressed the expression of D10 and Os01g0701500 in non‐mycorrhizal plants, while D27 and D17 remained stable. However, in mycorrhizal plants, cold stress triggered a marked upregulation of all these genes, suggesting that AMF enhance SL biosynthesis to improve plant tolerance under chilling conditions (Liu et al. 2015). These observations support the notion that SLs, possibly through AMF‐mediated signalling, contribute to maintaining cellular homeostasis under low temperatures. Nonetheless, the precise regulatory mechanisms underlying SL‐mediated cold tolerance remain incompletely understood and warrant further investigation.

At the molecular level, endogenous strigolactones contribute to the regulation of cold stress responses by modulating key signalling pathways involved in redox homeostasis and transcriptional control. Exogenous application of the synthetic SL analogue GR24 in Brassica rapa has been shown to induce the expression of genes encoding antioxidant enzymes, NADPH oxidases, mitogen‐activated protein kinases (MAPKs) and transcriptional regulators such as COR and ICE1, thereby enhancing ROS detoxification and promoting stress adaptation. However, these GR24‐induced effects should be interpreted cautiously, as they represent physiological activation of SL signalling and may not fully reflect the physiological roles of endogenous SLs (Zhang et al. 2020). Mutant studies further highlight that SL‐deficient Arabidopsis and Pisum sativum lines exhibit impaired photosynthesis and greater sensitivity to cold, confirming the critical role of SL signalling in maintaining photosynthetic stability under low temperatures (Cooper et al. 2018). Moreover, Arabidopsis d14 mutants (defective in SL perception) display pronounced freezing sensitivity, characterized by lower survival and higher ion leakage. Recent findings revealed that SLs promote cold tolerance by modulating transcription factors involved in cold response. The transcription factor WRKY41 suppresses the expression of DREB1, a key regulator of cold tolerance, by binding to its promoter. SLs, through the MAX2‐dependent SCF complex, facilitate WRKY41 degradation, thereby releasing DREB1 from repression and enhancing its expression (Wang et al. 2025).

From a physiological and biochemical perspective, cold stress hinders photosynthesis, reduces nutrient and water uptake, and induces excessive generation of ROS, resulted in oxidative disruption of cellular components. GR24 alleviates these influences by maintaining PSII quantum efficiency and decreasing ROS, particularly H₂O₂ and O₂^•⁻. It also enhances the accumulation of osmolytes, helping plants preserve cellular hydration under chilling circumstances (Omoarelojie et al. 2021; Hu et al. 2025). Likewise, GR24‐treated plants exhibit higher activities of antioxidants, elevated proline and protein contents, and reduced membrane damage, collectively contributing to enhanced cold tolerance.

SLs affect leaf formation and overall architecture when plants experience low‐temperature stress. In P. sativum, mutants deficient in SL synthesis or signalling produced more leaves following dark‐chilling exposure, indicating that SLs may regulate energy allocation and leaf initiation under stress (Cooper et al. 2018). Similarly, max4‐1 and max2‐1 mutants exhibited reduced rosette areas under chilling, stressing the role of SL in modulating leaves morphology and maintaining optimal development under stress (Cooper et al. 2018). Collectively, these findings highlight that strigolactones act as key hormonal mediators in cold stress adaptation, integrating molecular signalling with physiological and morphological adjustments. By modulating transcriptional networks, antioxidant capacity, osmolyte accumulation and developmental plasticity, SLs contribute to improved plant performance under chilling and freezing conditions. However, deeper insights into SL cross‐talk with further stress hormones such as ABA, ethylene and jasmonates will be essential to fully decipher their integrated role in cold stress tolerance.

3.3. Role of Strigolactones in Plant Responses to Nutrient Deficiency

The soil solution represents the main source from which plants obtain essential nutrients necessary for proper growth and high productivity. Environmental challenges, including drought, temperature variability and soil salinity, can indirectly cause nutrient stress by restricting nutrient availability and absorption. In response, SLs act as key regulators, orchestrating adaptive plant responses by shaping both shoot and root architecture and facilitating symbiotic associations with beneficial microorganisms (Wani et al. 2023).

Plants are highly receptive to soil nutrient status, especially P and exhibit marked increases in SL production and exudation under P‐deficient conditions, whereas P capability controls SL biosynthesis (Yoneyama 2019). Enhanced SL exudation under P starvation promotes AMF colonization, a symbiotic relationship that significantly improves P uptake and overall nutrient acquisition (Yoneyama 2019). Application of exogenous SLs has been shown to alleviate P deficiency in tomato and Arabidopsis by stimulating acid phosphatase activity, inducing P‐starvation marker genes, and promoting anthocyanin accumulation (Gamir et al. 2020). These responses highlight the cross‐communication between P‐starvation signalling and SL pathways. In Oryza sativa, SLs also enhance root growth under nutrient‐limited conditions, particularly when phosphate or nitrate levels are low (Sun et al. 2014). Positive correlations between primary root elongation and SL production have been documented in wheat, rice and tomato under P deficiency. Similarly, SLs contribute to the elongation of crown and seminal roots in rice during nutrient stress (Sun et al. 2014).

Interestingly, SLs exhibit dual regulation of root architecture depending on phosphate availability (Figure 6). Under sufficient Pi conditions, SLs suppress lateral root formation; however, under Pi limitation, they shift toward positive regulation, enhancing root proliferation and nutrient foraging capacity. In Arabidopsis, P deficiency inhibits shoot branching bud outgrowth via SL signalling, an effect absent in SL biosynthetic mutants (Kohlen et al. 2010). Moreover, Pi deficit increases SL synthesis and stability, possibly involving RSL4, a transcription factor linking SL–auxin crosstalk and root hair development. The TMO5/LHW heterodimer in tissues activates cytokinin biosynthesis, enhancing root hair density under low Pi by regulating epidermal cell elongation and fate (Wendrich et al. 2020). While phosphorus deficiency is the most studied trigger, deficiencies in N and S also stimulate SL biosynthesis and exudation. Nitrogen shortage enhances SL release in lettuce, maize and sorghum, while sulphur deficiency in rice induces the expression of specific SL biosynthetic genes (Yoneyama 2019). Notably, under S starvation, only the D27 gene is upregulated, whereas P deficiency induces the expression of the entire SL biosynthetic suite, suggesting that D27 performs a central function in S‐dependent AMF symbiosis.

Figure 6.

Schematic representation of strigolactone‐mediated plant responses to nutrient deficiency. [Color figure can be viewed at wileyonlinelibrary.com]

Beyond AMF, SLs are also involved in rhizobial symbiosis and nodulation in legumes such as soybean, contributing to enhanced N acquisition (Rehman et al. 2018). Crosstalk with other phytohormones particularly abscisic acid and auxin, acts as a positive regulator of SLs biosynthesis, although antagonistic interactions can occur under certain conditions (Parwez et al. 2022). Overall, the intricate interplay among SL biosynthetic pathways, phytohormone signalling, and nutrient availability is multifaceted and not yet fully elucidated. Further studoes is required to decode how these factors collectively regulate SL production, exudation and downstream signalling in plants. Recent evidence suggests that SLs modulate phosphate transporter activity, yet their role in heavy metal transport remains largely unexplored. Given their capacity to promote symbiotic associations with AMF and rhizobia, SLs could serve as promising agents in plant‐based remediation strategies, enhancing the uptake and detoxification of heavy metals from contaminated soils. However, detailed studies are still required to evaluate the mechanistic effectiveness and ecological safety of such treatments.

3.4. Strigolactones as Key Modulators of Plant Drought Stress Responses

Among abiotic stresses, water deficit is particularly widespread and detrimental. affecting crop productivity worldwide. Water scarcity disrupts physiological and biochemical processes, including photosynthetic carbon assimilation, ROS homeostasis and cellular osmotic balance, ultimately impairing growth and yield. Plants have evolved complex adaptive strategies, such as stomatal regulation, osmotic adjustment, antioxidant activation and root system remodelling to survive under limited water availability. Recent studies have established that SLs, a group of plant hormones originating from carotenoid precursors, act as key regulators in orchestrating drought tolerance through multifaceted molecular and physiological mechanisms (Figure 7).

Figure 7.

Schematic representation of the interplay among strigolactones (SLs), abscisic acid (ABA), auxin, and cytokinin (CK), along with associated regulatory components under drought stress. Drought conditions are associated with the induction of SL biosynthetic genes (e.g., D27, MAX3/CCD7, MAX4/CCD8), leading to SL accumulation. SLs interact with ABA biosynthesis and signaling pathways, specifically modulating the core ABA signalosome components (PYR/PYL/RCAR–PP2C–SnRK2), and are associated with the modulation of calcium‐dependent protein kinases (CDPKs) and SLAC1/SLAH3 channels, which may contribute to stomatal closure and reduced water loss. SL perception by the D14–MAX2 complex may influence BRC1‐mediated bud outgrowth. SLs are also linked to the modulation of CK signaling and PIN‐mediated auxin transport, potentially contributing to adaptive resource allocation under stress conditions. In roots, SLs are associated with lateral root modulation and may contribute to overall root system architecture adjustment in a species‐, tissue‐, and context‐dependent manner. Additionally, SLs are linked to the modulation of cell cycle‐related genes (PCNA, CycD, CDK), which may support root growth and water uptake during drought stress. [Color figure can be viewed at wileyonlinelibrary.com]

Under drought conditions, SL biosynthesis and signalling undergo dynamic modulation. Ruiz‐Lozano et al. (2016) demonstrated that drought stress downregulated SlCCD7 in Solanum lycopersicum, resulting in reduced SL levels, whereas application of the synthetic analogue GR24 restored drought tolerance by maintaining photosynthetic performance and reducing oxidative injury. Similarly, in Vitis vinifera, polyethylene glycol–induced drought stress elevated H₂O₂ and MDA content while decreasing chlorophyll levels, but GR24 treatment reversed these effects by enhancing antioxidant enzyme activities and chlorophyll stability (Min et al. 2019). Comparable trends were reported in Triticum aestivum, where GR24 application reduced lipid peroxidation and H₂O₂ accumulation, suggesting a protective role for SLs as ROS modulators (Sedaghat et al. 2017). Table 2 presents different examples of plant species responses to drought stress.

Table 2.

Strigolactone‐mediated responses of different plant species to drought stress.

Plant species	Effects of SLs	References
Grape (Vitis vinifera)	Increases: RWC; chlorophyll content and photosynthetic rate; antioxidant capacity. Decreases: stomatal opening; electrolyte leakage; H2O2 and MDA contents	Min et al. (2019)
Maize (Zea mays L.)	Increases: stomatal conductance; water use efficiency; gas exchange characteristics; net CO2 assimilation rate; chlorophyll content; antioxidant enzymes activities; leaf ascorbic acid; total phenolics; glycine betaine; free proline	Luqman et al. (2023)
Rice (Oryza sativa)	SL production is stimulated under drought, contributing to drought acclimation by modulating root–shoot signalling, stress‐responsive pathways and adaptive growth adjustments.	Haider et al. (2018)
Thale cress (Arabidopsis thaliana)	Upregulation of SL biosynthetic genes under drought and salinity suggests a key regulatory role of SLs in osmotic stress tolerance and ABA‐mediated adaptive responses.	Ha et al. (2014)
Tomato (Solanum lycopersicum)	SL levels are modulated by drought and arbuscular mycorrhizal symbiosis, indicating that SLs promote drought tolerance by enhancing root–microbe communication and nutrient acquisition.	Ruiz‐Lozano et al. (2016)
Tomato (Solanum lycopersicum)	Differential regulation of SL biosynthesis between roots and shoots under drought implies tissue‐specific roles of SLs in stress perception, hormonal crosstalk and resource reallocation.	Visentin et al. (2016)
Wheat (Triticum aestivum)	Increases: RWC; membrane stability index; POD, CAT and APX activities. Decreases electrolyte leakage; MDA content	Sedaghat et al. (2017)

Genetic analyses further confirm the crucial role of SL signalling in drought adaptation. Arabidopsis thaliana mutants defective in SL biosynthesis (max3 and max4) and perception (max2) exhibit accelerated water loss, impaired stomatal regulation and increased drought susceptibility (Ha et al. 2014). Li, Nguyen, Chu, et al. (2020) demonstrated that DWARF14 (D14), the canonical SL receptor, plays a direct and specific role in drought adaptation by modulating SL‐dependent gene expression, stomatal behaviour and stress‐responsive pathways in Arabidopsis thaliana. In contrast, Ha et al. (2013) primarily investigated the function of more axillary growth 2 (MAX2), an F‐box protein that acts as a central signalling hub in both strigolactone and karrikin pathways. While their work showed that MAX2 positively regulates drought and salt tolerance, its involvement cannot be attributed exclusively to SL signalling. Therefore, D14‐mediated responses represent SL‐specific mechanisms, whereas MAX2‐dependent responses reflect shared regulatory networks integrating SL and karrikin signalling under abiotic stress.

Exogenous GR24 restored drought tolerance in max3 and max4 mutants but not in max2, indicating that drought resistance depends on intact SL perception via the D14–MAX2 signalling module. In Oryza sativa, comparative analysis of SL mutants revealed reduced ABA content in d27, implicating OsD27 in regulating ABA biosynthesis and highlighting the close metabolic and signalling relationship between SLs and ABA (Haider et al. 2018). Similarly, hvd14.d mutants in Hordeum vulgare displayed hypersensitivity to drought, with lower relative water content, altered stomatal density, disrupted chloroplast ultrastructure, and reduced photosynthetic efficiency, attributed to impaired ABA metabolism and signalling (Marzec et al. 2020). Conversely, overexpression of D14 from Zea mays or GmMAX2a from Glycine max in Arabidopsis significantly enhanced drought tolerance (Nisa et al. 2023). At the molecular level, SL signalling regulates genes associated with photosynthesis, carbon metabolism and root growth. GR24 upregulates genes encoding key photosynthetic enzymes and root‐related metabolic genes in Pennisetum purpureum, enhancing carbon assimilation and energy balance under drought (Zhou et al. 2023). Moreover, smxl6,7,8 triple mutants of A. thaliana exhibit higher drought tolerance, with elevated anthocyanin synthesis, enhanced ABA sensitivity and upregulation of late embryogenesis abundant (LEA) genes (LEA/ABR, LEA18, LEA76), reinforcing SLs' role in activating downstream stress‐responsive pathways (Li, Nguyen, Tran, et al. 2020).

SLs also interact intricately with ABA signalling, forming a synergistic network controlling stomatal dynamics. Both hormones share a carotenoid‐derived biosynthetic origin and coordinate in regulating drought reactions. SL‐deficient mutants (max3, max4, Ljccd7‐silenced) and signalling‐deficient mutants (max2, Atd14, Slccd7) exhibit impaired ABA‐induced stomatal closure, leading to excessive transpiration and water loss (Visentin et al. 2016). GR24 application restores stomatal closure in biosynthetic but not perception mutants, confirming that ABA sensitivity requires intact SL perception. The slow anion channel‐associated 1 (SLAC1) serves a critical function in this regulation; SLs induce H₂O₂ and nitric oxide (NO) accumulation, which activate SLAC1 to trigger stomatal closure. In SLAC1 mutants, both ABA‐ and SL‐induced stomatal closure are disrupted, emphasizing the convergence of these signalling pathways on the same ion channel (Zhang et al. 2018). Moreover, jasmonic acid (JA) enhances SL‐ and ABA‐mediated closure by stimulating Ca²⁺ influx and activating calcium‐dependent protein kinases (CDPKs), indicating a multi‐hormonal regulatory network (Ha et al. 2014).

Although ABA is widely recognized as the primary hormonal signal controlling drought‐induced stomatal closure, accumulating evidence suggests that SLs function as critical modulators of ABA sensitivity rather than as simple downstream effectors. In several species, SL‐deficient or signalling‐impaired mutants exhibit reduced responsiveness to exogenous ABA, indicating that SL signalling is required for full ABA efficacy in guard cells. This positions SLs functionally downstream or parallel to ABA biosynthesis, where they amplify ABA‐induced ion fluxes, ROS production and Ca²⁺ signalling cascades. However, in other contexts, SLs appear to act upstream of ABA, regulating its biosynthesis and accumulation. For instance, reduced endogenous ABA levels in d27 mutants of rice and altered ABA homeostasis in barley hvd14.d mutants suggest that intact SL biosynthesis is necessary for proper ABA production under drought stress. Taken together, these findings indicate that SL–ABA interactions are not unidirectional but form a feedback‐regulated module in which SLs can either modulate ABA sensitivity at the signalling level or influence ABA accumulation itself. This dual positioning enables fine‐tuning of stomatal responses according to stress intensity, developmental stage and tissue specificity.

SLs confer drought tolerance through multiple physiological and biochemical adaptations. GR24 treatment reduces stomatal conductance and transpiration in Vitis vinifera, Triticum aestivum and Zea mays, thereby improving water‐use efficiency (Sedaghat et al. 2021). It also mitigates drought‐induced declines in chlorophyll content and photosynthetic rate across diverse species, including Malus hupehensis, Medicago sativa and P. purpureum (Xu et al. 2023). Concurrently, GR24 enhances antioxidant defence by stimulating the activities of SOD and APX, effectively reducing ROS accumulation and safeguarding cellular structures against oxidative damage injury (Sedaghat et al. 2021). Recent evidence confirms that SLs serve as a key regulator of mediating plant developmental and physiological adaptations to drought stress through the regulation of hormone signalling, osmoprotection and antioxidative defence. Yu et al. (2025) reported that treatment of the synthetic GR24 markedly enhanced drought tolerance in Zea mays seedlings. GR24 treatment improved leaf and root biomass, relative water content and chlorophyll accumulation, while significantly reducing malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and proline levels. Transcriptomic profiling revealed that GR24 activated plant hormone signal transduction and MAPK signalling pathways, contributing to improved osmotic adjustment, photosynthetic recovery and post‐stress survival. These findings highlight the ability of SLs to coordinate molecular and metabolic processes that sustain growth and accelerate recovery following rehydration. Complementary findings by Ghaderi et al. (2025) demonstrated that foliar application of SLs, especially when combined with selenium (Se) and forchlorfenuron (CPPU), mitigated drought‐induced declines in Stevia species. The Se + SLs + CPPU treatment enhanced relative water content, chlorophyll retention and antioxidants, resulting in higher leaves number and increased steviol glycoside (SvGls) accumulation, particularly in the Indian genotype. This integrated approach also improved osmoprotection and ROS detoxification, underscoring the synergistic effects of SLs with other growth regulators under water‐deficit conditions.

Osmotic adjustment is another hallmark of SL‐mediated drought resilience. GR24 promotes accumulation of proline, soluble sugars and other osmoprotectants that maintain cell turgor and protect macromolecules under dehydration (Sedaghat et al. 2021). Reduced MDA content and electrolyte leakage in GR24‐treated plants confirm its role in preserving membrane stability (Luqman et al. 2023; Xu et al. 2023). Additionally, SLs influence root system architecture to optimize water uptake: GR24 promotes primary root elongation, increases lateral root number and enhances root‐to‐shoot ratio in crops such as Festuca arundinacea, P. purpureum, M. sativa and wheat (Yang et al. 2023; Sedaghat et al. 2021). These morphological changes are linked to SL regulation of PIN‐mediated auxin transport and expression of cell cycle–associated genes such as Cyclin D2 and CDKB (Hu et al. 2018).

Root system remodelling is a critical adaptive response to water limitation, and this process is governed by tightly coordinated SL–auxin interactions. While auxin establishes local maxima that drives lateral root initiation and elongation, SLs function as long‐range modulators that reshape auxin fluxes by regulating the abundance and polarity of PIN‐FORMED (PIN) auxin transporters. Under drought stress, elevated SL signalling suppresses excessive lateral root formation while promoting primary root elongation, thereby favouring deep soil exploration. In this context, SLs act predominantly upstream of auxin redistribution, modulating directional auxin transport rather than auxin biosynthesis itself. However, auxin also feeds back to induce the expression of SL biosynthetic genes such as MAX3 and MAX4, creating a tightly coupled regulatory loop. This reciprocal regulation enables dynamic root architectural plasticity in response to fluctuating soil moisture conditions. Rather than acting as linear regulators, SLs and auxin form an interconnected module that balances growth restraint with stress exploration strategies.

Beyond intrinsic plant responses, SLs modulate interactions with beneficial microorganisms. Arbuscular mycorrhizal (AM) fungi, which rely on SLs as host‐derived signalling molecules, participate in enhanced drought tolerance through the promotion of root hydraulic conductivity and nutrient uptake. In S. lycopersicum and Lactuca sativa, lack of AM symbiosis led to lower SL production and increased ABA accumulation under drought, demonstrating that SL–AM signalling enhances drought tolerance through both hormonal and symbiotic pathways (Ruiz‐Lozano et al. 2016). Taken together, SLs function as central integrators of molecular and physiological responses that enable plants to withstand drought stress. Through interactions with ABA, JA and auxin pathways, SLs coordinate stomatal regulation, ROS detoxification, osmoprotection and root remodelling. These coordinated processes maintain photosynthetic activity, protect cellular integrity and optimize water usage under limited moisture conditions.

These findings support a conceptual shift in how SLs are viewed in drought adaptation. Rather than functioning as linear upstream or downstream regulators, SLs operate as dynamic network integrators that recalibrate hormonal sensitivity, transcriptional responsiveness and developmental outputs. Through context‐dependent interactions with ABA, auxin and jasmonates, SLs fine‐tune stomatal behaviour, root architecture, ROS signalling and osmoprotectant metabolism. This network‐based framework better reflects the biological reality of stress adaptation, in which multiple hormonal pathways converge on shared downstream targets such as ion channels, transcriptional regulators and redox hubs. By modulating signal amplitude rather than acting as binary switches, SLs enable plants to balance growth and survival under fluctuating drought conditions. Future research should aim to elucidate the downstream transcriptional networks and post‐translational regulators of SL signalling in guard cells and roots, and to explore the biotechnological potential of manipulating SL pathways to enhance drought resilience in major crops.

3.5. Strigolactones as Key Modulators of Plant Responses to Light‐Related Stress

Light is an indispensable yet complex environmental signal that governs nearly every aspect of plant development, from germination to flowering. Unlike other abiotic stresses, light cannot be avoided or minimized; plants must continuously perceive, interpret and adapt to fluctuating light conditions. Excessive, insufficient, or imbalanced light intensity can induce physiological stress, disrupt photosynthetic performance and alter hormonal signalling networks. Recent findings highlight that SLs are closely integrated into light signalling pathways, acting as modulators of photomorphogenesis and adaptive growth under varying light environments.

Evidence indicates that SL levels are dynamically regulated by light quality and intensity, suggesting a strong interconnection between SL biosynthesis and photosensory signalling. The Pleiotropic Photosignaling (PPS) gene, which encodes the F‐box protein MAX2/ORE9, serves a vital function in mediating light responses and photomorphogenic advancement. In Arabidopsis thaliana, PPS mutants exhibit reduced sensitivity to blue, red and far‐red light, leading to elongated hypocotyls and impaired photomorphogenesis. This phenotype underscores the importance of the MAX2‐dependent SL pathway in coordinating light perception and downstream growth responses. SLs suppress hypocotyl elongation in a manner dependent on light, a process that involves ELONGATED HYPOCOTYL 5 (HY5), a key transcription factor in light signalling. HY5 functions as a negative regulator of hypocotyl growth and SLs contribute to increased HY5 stability and accumulation, thereby reinforcing its inhibitory effect. Treatment of GR24 restored the elongated hypocotyl phenotype of hy1 and hy2 mutants, but not hy5, suggesting that SL signalling operates through a HY5‐dependent mechanism (Tsuchiya et al. 2010).

The interplay between SLs and constitutive photomorphogenic 1 (COP1) further supports their role in light signalling. COP1 promotes hypocotyl elongation in darkness by degrading HY5. However, GR24 treatment triggers nuclear exclusion of COP1, thereby preventing HY5 degradation and enhancing photomorphogenic development even under dark or low‐light conditions. This demonstrates that SLs can partially mimic or supplement light signalling, functioning as photomorphogenic modulators when light intensity is insufficient (Tsuchiya et al. 2010). At the transcriptional level, SLs interact with phytochrome A‐mediated light signalling. This upregulation promotes shoot branching by attenuating SL action. These intricate interactions highlight how light, and SLs converge on common molecular nodes to fine‐tune shoot architecture and plant morphology.

In monocots such as rice, phytochromes regulate light absorption and inhibit mesocotyl elongation, a trait particularly sensitive to light availability. Disruption in SL biosynthesis or signalling enhances mesocotyl elongation under darkness, suggesting that SLs counteract shade‐induced elongation growth. Studies on SL‐deficient (d10‐1, d17‐1, d27‐1) and SL‐insensitive (d14, d3) rice mutants demonstrated that GR24 treatment suppresses mesocotyl elongation observed in biosynthesis‐deficient mutants, yet absent in signalling‐defective mutants, confirming that this regulation requires an intact SL perception system (Hu et al. 2010). Moreover, SLs intersect with CK signalling to control mesocotyl growth. In O. sativa mutants (d10‐1, d14‐1), CK‐responsive type‐A Response Regulator genes exhibited elevated expression levels under darkness, whereas the growth‐repressing gene OsTCP5 was downregulated. GR24 application restored OsTCP5 expression in d10‐1 but not in d14‐1, demonstrating that SLs repress mesocotyl elongation through a CK–SL interaction network dependent on downstream SL signalling (Hu et al. 2014).

Light stress also disrupts photosynthetic homeostasis, leading to metabolic imbalance. In tomato, exposure to low light intensity impaired photosynthetic characteristics and assimilative metabolism, resulting in reduced carbon fixation and energy availability. Interestingly, exogenous GR24 application restored photosynthetic efficiency, stabilized metabolic profiles and improved overall plant performance under low‐light stress, suggesting that SLs enhance light utilization and mitigate photoinhibition (Lu et al. 2019). Collectively, these findings reveal that strigolactones are integral components of the light signalling network, acting in coordination with photoreceptors, transcriptional regulators and hormonal pathways. By modulating photomorphogenic growth, shoot branching and photosynthetic efficiency, SLs help plants optimize light perception and maintain developmental balance under both low‐ and high‐light stress conditions. Future studies should emphasis on elucidating the precise molecular crosstalk between SLs and photoreceptor pathways, particularly their interactions with phytochromes, cryptochromes and circadian regulators, to better understand how plants adapt to fluctuating light environments under changing climatic scenarios.

3.6. Strigolactone‐Mediated Regulation of Plant Adaptation to Salinity Stress

Soil salinization is increasingly recognized as a leading global threat to agricultural sustainability and environmental stability, severely threatening crop productivity and food security (Al‐Khayri et al. 2024). It is estimated that more than 7% of the world's terrestrial area is currently affected by salinity, and this proportion is projected to approach 50% by the middle of the twenty‐first century due to the combined effects of climate change, poor irrigation management and rising sea levels (Huang et al. 2025). Salinity imposes multiple constraints on plant physiology, including osmotic and ionic imbalances, nutrient deficiencies, oxidative damage and growth retardation. Elevated levels of Na⁺ and Cl⁻ in the rhizosphere disrupt cellular homeostasis, impair water uptake and interfere with vital metabolic procedures such as photosynthesis and respiration, ultimately leading to reduced biomass accumulation and yield. To counter these detrimental effects, plants activate a suite of adaptive responses encompassing osmotic adjustment, selective ion transport, biosynthesis of compatible solutes (such as proline and glycine betaine) and activation of antioxidant defence systems to detoxify reactive oxygen species. Additionally, hormonal crosstalk particularly involving ABA, auxins, cytokinins and jasmonates plays a pivotal role in coordinating stress perception and signalling pathways that fine‐tune gene expression and physiological adjustments under saline conditions. In recent years, SLs, a class of carotenoid‐derived terpenoid lactones, have gained prominence as multifunctional signalling molecules that integrate developmental regulation with environmental adaptability. Initially identified as germination stimulants and regulators of shoot branching, SLs are now recognized as central mediators of plant reactions to abiotic stresses, including salinity. Mounting evidence demonstrates that SLs contribute to salt stress tolerance through a network of interconnected mechanisms: enhancing antioxidant capacity, regulating ion transporters to maintain Na⁺/K⁺ homeostasis, modulating hormonal signalling (notably ABA and ethylene), and activating stress‐responsive genes (Ren et al. 2018; Aroca et al. 2013; Ling et al. 2020). Although breeding and genetic engineering approaches have been explored to develop salt‐tolerant cultivars, these strategies remain expensive, time‐consuming and technically demanding. Thus, attention has increasingly turned toward phytohormone‐mediated tolerance mechanisms as sustainable and eco‐friendly alternatives. Among these, SLs have recently emerged as pivotal regulators of salt stress tolerance (Yu et al. 2022). Evidence suggests that strigolactones enhance plant adaptation to salinity by reshaping root structure and growth patterns, photosynthetic efficiency, antioxidant capacity, osmolyte accumulation and ion balance (Table 3).

Table 3.

Strigolactone‐mediated improvements in plant salt stress resistance.

Plant	Effects of SLs under stress	References
Arabidopsis (Arabidopsis thaliana)	SLs enhanced adaptive mechanisms under osmotic stress by regulating physiological responses and improving stress resilience.	Ha et al. (2014)
Black goji berry (Lycium ruthenicum)	GR24 improved plant growth, cell vitality, chlorophyll fluorescence, AsA–GSH cycle activity and chloroplast ultrastructure, activating genes involved in stress metabolism and signalling.	Huang et al. (2025)
Branched broomrape (Orobanche ramosa)	SL biosynthesis during AMF association enhanced photosystem II efficiency, stomatal regulation and growth under salinity.	Aroca et al. (2013)
Canola (Brassica napus)	GR24 improved shoot and root growth, mitigating salinity‐induced suppression of biomass.	Ma et al. (2017)
Maize (Zea mays)	Combined GR24 and melatonin treatment strengthened antioxidant defences, osmotic adjustment and K⁺/Na⁺ homeostasis, reducing oxidative injury.	Aloufi et al. (2025)
Rice (Oryza sativa)	GR24 improved photosynthetic rate, stomatal conductance and chlorophyll content, enhancing rice tolerance to NaCl stress.	Ling et al. (2020)
Sesbania (Sesbania sesban)	SL accumulation driven by H₂O₂ signalling and AMF symbiosis improved ion balance and salt tolerance.	Kong et al. (2017)
Sunflower (Helianthus annuus)	Foliar‐applied GR24 alleviated salt‐induced growth inhibition, increasing transpiration, osmotic potential and relative water content.	Sarwar and Shahbaz (2020)
Sunflower (Helianthus annuus)	GR24 enhanced callus growth, protein synthesis and antioxidant enzyme activity under saline conditions.	Zulfiqar et al. (2021)
Thale cress (Arabidopsis thaliana)	SLs induced stomatal closure and osmotic adjustment, improving water conservation under saline stress.	Lv et al. (2017)
Tobacco (Nicotiana tabacum)	SLs coordinated with ROS and ABA to mediate systemic priming of salt tolerance between connected tobacco plants.	Zheng et al. (2025)
Tomato (Solanum lycopersicum)	SL treatment improved H⁺‐ATPase activity, enhanced K⁺ retention, reduced Na⁺ accumulation and modulated carbohydrate metabolism via H₂S‐dependent signalling.	Khan et al. (2025)
Wheat (Triticum aestivum)	GR24 enhanced CO₂ assimilation and growth, improving salt resilience through antioxidant activation.	Kausar and Shahbaz (2017)
Wheat (Triticum aestivum)	Exogenous GR24 boosted antioxidant enzyme activities (APX, CAT, PPO), maintained Na⁺/K⁺ balance, increased proline and chlorophyll contents, and regulated stress‐responsive genes (TaSOS1, HKT1).	Jariani et al. (2025)
Woodland sage (Salvia nemorosa)	GR24 improved chlorophyll, gas exchange, proline accumulation, antioxidant enzyme activities and essential oil yield under salt stress.	Sharifi and Bidabadi (2020)

In addition to direct physiological regulation, SLs significantly influence the establishment and regulation of plant–microbe associations under saline conditions. Plants frequently establish mutualistic symbioses with arbuscular mycorrhizal (AM) fungi, which can significantly improve stress tolerance. Under nutrient‐deficient or saline conditions, plants exude signalling molecules, most notably SLs that act as chemical cues to attract AM fungi and stimulate hyphal branching (Andreo‐Jimenez et al. 2015). This symbiosis not only enhances nutrient and water but also improves osmotic adjustment through the accumulation of osmoregulators, thereby mitigating salinity‐induced damage (Kong et al. 2017). In this context, SLs can be viewed as “cry‐for‐help” signals, coordinating both internal hormonal adjustments and external microbial partnerships to reinforce plant resilience (Figure 8).

Figure 8.

Strigolactone‐mediated regulation of plant adaptation to salinity stress. [Color figure can be viewed at wileyonlinelibrary.com]

Experimental evidence further supports the defensive role of SLs versus salinity. For instance, the exogenous treatment of GR24 has been shown to alleviate salt‐induced inhibition of photosynthesis in Brassica napus (Ma et al. 2017). Mutant analyses in Arabidopsis thaliana showed that max3 and max4 are markedly more sensitive to salinity during germination and vegetative stages (Ha et al. 2014), highlighting the intrinsic link between SL signalling and salt tolerance. Similar results have been observed in cereals: in Oryza sativa, GR24 application reduced salt‐induced ROS and MDA accumulation, thereby maintaining cellular integrity and normal seedling growth (Ling et al. 2020). In Triticum aestivum, GR24‐treated cultivars exhibited enhanced growth compared to untreated controls under saline conditions (Kausar and Shahbaz 2017). Beyond major crops, SL‐mediated salinity tolerance has also been reported in aromatic and oilseed plants. In Salvia nemorosa, GR24 treatment reduced MDA and H₂O₂ accumulation while enhancing essential oil yield under salinity stress (Sharifi and Bidabadi 2020).

SLs function as primary mediators of plant adaptation to salinity, not only through direct physiological regulation but also by mediating symbiotic interactions with arbuscular mycorrhizal fungi (AMF). Under saline conditions, the interaction between SLs and other hormones, particularly ABA is fundamental to modulating adaptive responses and promoting AMF establishment. Ren et al. (2018) demonstrated that supplementation via external means of ABA, NaCl and H₂O₂ significantly upregulated the expression of CCD7 and CCD8 (key SL biosynthetic genes in roots) and MAX2 (in shoots) in Sesbania cannabina. Conversely, treatment with tungstate and dimethylthiourea (DMTU), a hydrogen peroxide scavenger, suppressed CCD7 and CCD8 expression in AMF‐related plants under stress. Moreover, ABA‐persuaded SL assembly was blocked when plants were pre‐treated with DMTU or TIS108, an SL biosynthesis inhibitor, suggesting that ABA‐driven H₂O₂ signalling is critical for AMF‐persuaded SL synthesis under salinity. Similar correlations have been observed in AMF‐inoculated L. sativa, where both SL and ABA biosynthetic gene expression were elevated under salinity, resulting in improved biomass and stomatal conductance (Aroca et al. 2013). These findings highlight a synergistic relationship between SLs and ABA during AMF symbiosis that enhances salinity tolerance through integrated physiological and metabolic adjustments.

At the molecular level, SLs exert multifaceted control over the transcription of genes involved in photosynthesis, antioxidant defence and ion transport, thereby coordinating plant adaptive responses under saline conditions. In Brassica napus L., exogenous application of GR24 significantly modifies the transcriptional profiles of genes governing photosynthesis, tryptophan metabolism and multiple phytohormonal pathways, enhancing overall tolerance to salt stress (Ma et al. 2017). Likewise, in cucumber, GR24 treatment improves the expression of antioxidant enzyme–encoding genes and key components of redox and ionic signalling networks, including NADPH oxidase, CDPKs and calcineurin B‐like protein 3 (CBL3). These molecular activations fortify ionic balance and redox homeostasis, key determinants of salinity tolerance. Gene expression profiling further indicates that GR24 triggers H₂O₂‐dependent and MAPK‐mediated signalling cascades, underscoring the pivotal role of SLs in orchestrating interconnected stress signalling networks.

SL biosynthesis and signalling are inherently dynamic and stress‐responsive. Exposure to saline conditions upregulates crucial SL biosynthetic genes such as carotenoid cleavage dioxygenase 7 and 8 (CCD7, CCD8) and signalling regulators like more axillary growth 2 (MAX2). In Sesbania cannabina, both salinity and application of ABA or H₂O₂ markedly increase the expression of CCD7, CCD8 and MAX2, resulting in enhanced endogenous SL production and improved stress adaptation (Ren et al. 2018). Conversely, inhibition of SL biosynthesis or ROS scavenging dampens these transcriptional responses, suggesting a reciprocal regulatory loop between ABA, ROS and SL signalling. This interplay underscores the interdependence of hormonal and redox cues in fine‐tuning plant stress responses. Consistently, Arabidopsis max2 mutants display heightened salt sensitivity, reduced antioxidant capacity and impaired signal transduction, further confirming the essential role of MAX2 in maintaining SL‐mediated adaptive responses (Ha et al. 2014). Salinity stress triggers complex signalling networks involving nitric oxide (NO), ROS and Ca²⁺, which converge to activate SL biosynthetic and downstream pathways, thereby reducing injury. During this process, ABA‐responsive element‐binding proteins/factors are phosphorylated by SNF1‐related protein kinase 2 (SnRK2s), initiating ABA‐dependent gene expression. The promoters of major SL biosynthetic and signalling genes, contain ABA‐responsive element motifs, indicating direct regulation by ABA‐mediated transcriptional mechanisms (Yu et al. 2022). Consistent with this, Ha et al. (2014) reported a four‐ to eightfold increase in MAX3 and MAX4 transcripts within 10 h of ABA exposure, confirming ABF‐mediated activation of SL biosynthesis. This interaction initiates a self‐reinforcing regulatory cycle wherein ABA induces SL biosynthesis, and SLs in turn amplify antioxidant enzyme activities (SOD, POD), enhance CO₂ assimilation and lower MDA accumulation, protecting cells from oxidative injury and maintaining metabolic equilibrium under salt stress.

At the physiological level, SLs operate as essential drivers of sustaining photosynthetic performance and water‐use efficiency under saline conditions. Salinity often induces stomatal closure, chlorophyll degradation and reductions in CO₂ assimilation, collectively suppressing energy production and growth. Application of GR24 counteracts these detrimental effects by improving chlorophyll retention, stomatal conductance and net photosynthetic rate in diverse crops, including Brassica napus, rice, Salvia nemorosa, tomato and maize (Ling et al. 2020; Liu et al. 2022; Faisal et al. 2023; Sharifi and Bidabadi 2020). These improvements suggest that SLs help maintain carbon fixation efficiency and optimize transpiration and gas exchange, partly through their regulatory influence on ABA‐dependent stomatal signalling.

At the biochemical level, salinity triggers excessive ROS such as O₂^{• –} and H₂O₂, leading to lipid peroxidation, protein oxidation and nucleic acid injury. SLs mitigate these effects by improving the antioxidant defence system. GR24‐treated plants exhibit elevated activities of SOD, POD and GR, resulting in marked reductions in H₂O₂ and MDA contents. Such responses have been widely reported in many crops (Zulfiqar et al. 2021; Faisal et al. 2023; Mehrabi et al. 2024; Li et al. 2023). By re‐establishing redox homeostasis, SLs preserve membrane integrity, limit oxidative injury and support metabolic stability, contributing to sustained growth under saline environments.

A critical component of salinity tolerance is ion homeostasis. Excessive sodium (Na⁺) accumulation disrupts the K⁺/Na⁺ balance, inhibits enzymatic activities and compromises cytoplasmic functions. SLs assist in re‐establishing ionic equilibrium by promoting the uptake and retention of K⁺ and Ca²⁺ while restricting Na⁺ influx. For example, GR24‐treated sunflower and maize plants exhibit higher K⁺ and Ca²⁺ and lower Na⁺ concentrations compared to untreated controls (Zulfiqar et al. 2021). In bread wheat, GR24 maintains a favourable K⁺/Na⁺ ratio, correlating with improved growth and physiological resilience under saline conditions (Mehrabi et al. 2024). Additionally, SLs facilitate the deposition of stress‐related metabolites, including proline, which function both as osmoprotectants and ROS scavengers. Enhanced proline levels have been observed in Salvia, sunflower, cucumber, tomato and wheat following GR24 treatment (Faisal et al. 2023; Zulfiqar et al. 2021; Mehrabi et al. 2024), supporting osmotic adjustment and water retention.

The synergistic relationship among SLs, AMF and ABA further reinforces crop resilience to salinity. Studies in Lactuca sativa and Sesbania cannabina demonstrate that AMF‐inoculated plants exhibit improved photosynthetic efficiency, reduced photorespiration and lower ROS accumulation compared to non‐mycorrhizal controls (Aroca et al. 2013). Elevated ABA concentrations in both colonized and non‐colonized roots under salinity indicate a tight hormonal interconnection (Parwez et al. 2022). In plants treated with ABA biosynthesis inhibitors show markedly reduced SL levels, underscoring the central role of ABA in regulating SL synthesis. Moreover, the H₂O₂‐induced upregulation of SL biosynthesis in Sesbania cannabina (Ren et al. 2018) suggests that ABA‐generated H₂O₂ acts as a secondary messenger, amplifying SL synthesis during AMF‐mediated stress responses. However, the genetic components and transcriptional regulators underlying this ABA–H₂O₂–SL axis remain to be fully elucidated.

Beyond hormonal and symbiotic signalling, SLs also influence morphological adaptation under salinity. Salt stress typically inhibits root elongation, shoot expansion and biomass accumulation due to osmotic and ionic toxicity. GR24 application mitigates these effects by enhancing root branching, shoot elongation and overall vigour in B. napus, sunflower, rice and tomato (Ling et al. 2020; Sarwar and Shahbaz 2020; Liu et al. 2022; Faisal et al. 2023). The stimulation of root system architecture enhances nutrient uptake and ion compartmentalization, supporting cytoplasmic stability and long‐term adaptation to salinity. In Oryza sativa, GR24 restored plant height, root length and photosynthetic performance (Ling et al. 2020), while in Triticum aestivum, GR24 improved chlorophyll fluorescence under stress. Similarly, pre‐sowing GR24 treatment in sunflower significantly increased biomass, shoot length and K⁺/Na⁺ balance (Zulfiqar et al. 2021). Collectively, these findings demonstrate that strigolactones act as multifunctional integrators of physiological, biochemical and molecular processes under salinity stress. Through intricate crosstalk with ABA, ROS and symbiotic signalling networks, SLs coordinate photosynthetic regulation, antioxidant defence, osmotic adjustment and growth remodelling. This holistic regulation underscores their potential as biotechnological and agronomic targets for engineering salt‐tolerant plant varieties, offering a sustainable approach to mitigate the impacts of soil salinization in an era of increasing climate variability.

3.7. Strigolactone‐Mediated Regulation of Oxidative Stress in Plants

In all aerobic organisms, a delicate balance exists between the production of ROS and the scavenging activities of antioxidants. Oxidative stress occurs when this equilibrium shifts toward abnormally high ROS accumulation, triggering oxidative damage and disruption of cellular homeostasis (El‐Beltagi, Abdel‐Haleem, Adel, et al. 2025; El‐Beltagi, Gad, et al. 2025). In plants, ROS are continuously generated as unavoidable by‐products of aerobic metabolism and various biochemical reactions involving the partial reduction of molecular oxygen (El‐Beltagi, Abdel‐Haleem, Khedr, et al. 2025). The major forms of ROS include ¹O₂, O₂⁻, H₂O₂ and ^•OH. While these molecules can act as potent oxidants capable of damaging biomolecules, they also serve as essential signalling intermediates that regulate development, and defence mechanisms (Chaki et al. 2020). Thus, ROS possess a dual nature in plant biology, both destructive oxidants and vital regulators of signalling networks.

Under normal physiological conditions, plants maintain ROS at controlled levels through a finely tuned antioxidant defence system, consisting of enzymatic antioxidants such as SOD, CAT, POD and APX, as well as non‐enzymatic molecules like ascorbate, glutathione and carotenoids. However, when plants encounter abiotic or biotic stressors, including high salinity, drought, extreme temperatures, ultraviolet radiation, air pollutants, or heavy metals, ROS generation exceeds the detoxification capacity of antioxidants (EL‐Beltagi and Khedr 2025). This imbalance leads to redox disequilibrium, causing lipid peroxidation, nucleic acid damage and ultimately nitro‐oxidative stress, which can impair plant growth, metabolic function and crop yield (Chaki et al. 2020).

At the cellular and molecular level, ROS are generated in multiple organelles, notably chloroplasts, mitochondria and peroxisomes, during photosynthesis, respiration and photorespiration. Each of these compartments maintains distinct redox conditions that are dynamically interconnected through ROS signalling networks. Superoxide anions and H₂O₂ are relatively stable and diffuse across membranes, allowing them to function as mobile signalling molecules. However, when they undergo conversion into the highly reactive ^•OH via the Haber–Weiss or Fenton reactions, often catalysed by transition metals, they become extremely damaging rapidly reacting with nucleic acids and leading to irreversible cellular injury (Chaki et al. 2020). Excessive accumulation of H₂O₂ has been shown to trigger autophagy in chloroplasts to induce programmed cell death (PCD) within plant responses associated with stress defence and senescence. Such activities, while potentially detrimental under chronic stress, can also serve protective roles by removing damaged organelles and preventing the spread of oxidative lesions. Despite their potential toxicity, ROS are also indispensable secondary messengers in numerous signalling cascades. For instance, during pathogen attack or elicitor perception, plants experience a rapid and transient oxidative burst, a sharp increase in ROS levels that contributes to the hypersensitive response (HR) and fortification of cell walls through lignin formation and cross‐linking of hydroxyproline‐rich glycoproteins (Chaki et al. 2020). Additionally, ROS signalling activates the transcription of defence‐related genes and stimulates small antimicrobial compounds crucial for pathogen resistance.

Therefore, ROS represent a double‐edged sword: at low and tightly controlled stages, they purpose as key signalling particles that control development, hormone signalling and stress adaptation; yet at elevated levels, they inflict oxidative stress and compromise plant viability. The fine regulation of ROS homeostasis through continuous interplay between their generation and scavenging is central to redox signalling networks that integrate environmental cues with metabolic responses. Given the intensifying impact of climate change, with rising temperatures, increased salinity and drought frequency, understanding ROS dynamics has become crucial for improving plant resilience. Maintaining redox equilibrium is not only essential for sustaining photosynthesis, energy metabolism and cellular integrity but also for modulating broader stress signalling networks involving hormones such as ABA, SA and SLs. The latter, as emerging regulators, interact with ROS molecular signalling routes that adjust defence strategies and alleviate oxidative stress a relationship explored in the following section.

3.8. Strigolactone‐Mediated Regulation of Plant Responses to Heavy Metal Toxicity

Heavy metal contamination is recognized as the second most severe global environmental threat after salinity, posing substantial risks to both ecosystem function and food security. These metallic elements, including cadmium (Cd), arsenic (As), lead (Pb) and mercury (Hg), persist in soils and enter plant tissues, where they disrupt physiological, biochemical and molecular processes. Toxic metal accumulation results in growth retardation, photosynthetic inhibition, oxidative damage and nutrient imbalance, ultimately affecting productivity and food safety. However, plants have evolved intricate defence mechanisms, and phytohormones such as SLs play pivotal roles in orchestrating these adaptive responses.

3.8.1. SL‐Mediated Mitigation of Cadmium Toxicity

Cd is recognized as a highly phytotoxic heavy metal, known to impair chlorophyll biosynthesis, photosynthetic efficiency and antioxidant enzyme activities, while increasing the accumulation of ROS (Tai et al. 2017). Exogenous application of GR24, a synthetic analogue of strigolactone, has been reported to restore growth and photosynthetic performance under Cd stress. In Panicum virgatum, GR24 enhanced chlorophyll content, antioxidant enzyme activities and biomass accumulation, while reducing Cd uptake and ROS production (Tai et al. 2017).

Recent innovations have shown that nano‐formulated SL systems can further enhance plant tolerance to metal toxicity. For instance, SL‐conjugated biosilica nanoparticles (SL‐SiO₂ NPs) significantly reduced Cd accumulation in Brassica napus by promoting cell wall sequestration and vacuolar compartmentalization of Cd ions, leading to improved plant height, leaf area and PSII efficiency (Ali et al. 2025). The treatment also enhanced nutrient uptake and antioxidant defence, decreasing H₂O₂, O₂^•⁻ and MDA levels by upregulating the expression of genes encoding SOD, POD and chlorophyll biosynthetic enzymes (BnaCHLG, BnaCAO). Subcellular localization studies confirmed that SL‐SiO₂ NPs increased cell wall binding capacity for Cd by up to 50%, minimizing Cd translocation to sensitive organelles. These findings demonstrate that SL‐based nanoprotectants not only mitigate metal‐induced toxicity but also preserve cellular integrity through redox homeostasis and enhanced metabolic regulation.

3.8.2. Molecular Basis of SL‐Induced Heavy Metal Tolerance

Strigolactones affect the molecular expression patterns of both metal transporter and antioxidant‐associated genes, thereby modulating uptake and detoxification pathways. In Oryza sativa, SL‐deficient mutants (d10 and d17) displayed heightened sensitivity to arsenic (As) stress, with elevated As accumulation and reduced antioxidant capacity (Mostofa et al. 2021). Wild‐type plants exhibited higher expression of antioxidant genes such as OsCuZnSOD1, OsAPX1 and OsCATA, whereas mutants upregulated phosphate transporter genes (OsPT1, OsPT2, OsPT4, OsPT8), which facilitate arsenate (As⁵⁺) uptake due to its structural similarity to phosphate (Li et al. 2016). These results indicate that SLs help regulate metal–nutrient cross‐talk, maintaining phosphate homeostasis while restricting arsenic uptake. SL biosynthesis is known to be triggered under nutrient deficiency, particularly of phosphate and nitrogen, which often coincide with heavy metal stress conditions. Upregulation of SL biosynthetic genes like D10, D17, D27 and MAX1 under stress may facilitate adaptive responses by modulating root architecture and activating metal detoxification pathways (Ren et al. 2018). Moreover, the MAX2 signalling component plays a central role, as max2 mutants exhibit hypersensitivity to oxidative and ionic stress, emphasizing that SL signalling is crucial for coordinating redox balance and metal detoxification.

3.8.3. SLs in Regulating Oxidative and Antioxidant Responses Under Heavy Metals

Heavy metal stress triggers excessive production of ROS, which damage proteins and DNA. SLs mitigate this oxidative burden by improving antioxidant enzyme activities and reducing ROS accumulation. In Cd‐stressed barley, GR24 treatment reduced Cd uptake and ROS accumulation while boosting SOD, CAT and APX activities (Qiu et al. 2021). Similarly, exogenous SL application improved Cd tolerance in Gladiolus grandiflorus by enhancing chlorophyll content, relative water content and antioxidant capacity while decreasing lipid peroxidation and oxidative injury (Ahsan et al. 2025). Further, in wheat, SL application decreased Cd uptake and improved ROS‐scavenging efficiency, resulting in lower MDA accumulation and restored photosynthetic pigment levels (Shah et al. 2023). Such evidence underscores the synergistic role of SLs in regulating redox signalling, enhancing antioxidant defences, and preserving photosynthetic integrity under metal‐induced stress.

3.8.4. SLs, Ion Homeostasis and Phytohormonal Cross‐Talk

Heavy metal toxicity disturbs ionic equilibrium by displacing essential cations like Ca²⁺, Mg²⁺ and K⁺, and by disrupting membrane potential. SLs help maintain ionic homeostasis through the regulation of transporter activities and hormone‐mediated signalling cascades. SLs interact with auxins, ABA and CKs to balance nutrient uptake and cellular detoxification processes. For example, SL‐induced enhancement of ABA accumulation under stress conditions promotes stomatal closure, minimizing metal uptake via transpiration flow. Simultaneously, SL–auxin interactions regulate root elongation and lateral branching, optimizing root morphology for selective ion acquisition (Sharma et al. 2024).

3.8.5. Emerging Role of SL‐Based Nanotechnology

The integration of nanotechnology into plant stress biology has opened new frontiers for improving heavy metal tolerance. The recent use of strigolactone‐biosilica nanoparticles demonstrates a powerful synergistic approach for enhancing Cd sequestration and reducing metal toxicity in crops (Ali et al. 2025). These nanoparticles act as controlled‐release systems, delivering SLs efficiently to target tissues, thereby modulating metal chelation, antioxidant enzyme activities, and vacuolar sequestration mechanisms. Such nanotechnological innovations offer promising eco‐sustainable strategies for mitigating heavy metal contamination in agricultural soils under changing climate conditions.

4. Strigolactone Application Methods and Their Physiological Impacts

The efficiency of SLs in enhancing plant resilience against abiotic stresses is strongly influenced by their application method, concentration, plant species and stress type. Over the past few years, important insights have emerged regarding the structural diversity and biological properties of naturally occurring SLs, alongside the synthesis of potent analogues such as GR24. These analogues have been applied through various delivery systems including foliar sprays, nutrient or hydroponic solutions and tissue culture media, optimizing uptake, distribution and bioactivity. The chosen method directly affects absorption efficiency, systemic movement, and the magnitude of physiological and molecular responses (Figure 9). While endogenous SL production can be disrupted under adverse environmental conditions, exogenous application of synthetic SLs serves as a practical strategy to restore SL function, modulate stress‐related signalling, and improve growth and development under stress.

Figure 9.

Overview of strigolactone (SL) application methods and their main physiological impacts on plants under abiotic stress. (A) solution and hydroponic applications; (B) foliar sprays; and (C) in vitro and medium‐based applications. [Color figure can be viewed at wileyonlinelibrary.com]

4.1. Solution and Hydroponic Applications

Applying SLs through nutrient or Hoagland solutions provides a controlled environment for consistent root exposure and precise concentration management, making it an effective approach for both physiological and mechanistic studies. Liu et al. (2015) demonstrated that treating Lotus japonicus with 5.0 μM GR24 under osmotic and phosphorus deficiency enhanced the expression of LjPDR1 isoforms, while reducing ABA levels and the expression of ABA biosynthetic (LjNCED2) and catabolic (LjAAO3) genes. Similarly, Xu et al. (2015) reported that 2 μM GR24 modulated tiller bud development in Oryza sativa by upregulating FC1 and OsIPT expression while suppressing auxin transport‐related genes such as OsPIN9.

Under salinity conditions, hydroponic GR24 treatments have been shown to promote photosynthetic efficiency and antioxidant responses. For instance, Kausar and Shahbaz (2017) found that Triticum aestivum treated with 0.001–0.1 mg L⁻¹ GR24 exhibited enhanced CO₂ assimilation and stomatal conductance, while Ma et al. (2017) observed enhanced photosynthetic performance and antioxidants in Brassica napus under similar treatments. Moreover, in Panicum virgatum, exposure to 1 μmol L⁻¹ GR24 increased root growth, chlorophyll content and micronutrient uptake (Fe, Cu, Zn), while lowering ROS and cadmium accumulation (Tai et al. 2017). Solution‐based SL applications are particularly suited for mitigating stresses linked to nutrient imbalance, salinity and heavy metal toxicity. The intimate contact between SL molecules and root tissues enables effective signalling, which enhances ion homeostasis, antioxidative defence and metabolic stability. While highly effective in controlled environments, solution‐based SL applications face challenges for field translation, including maintaining stable SL concentrations in soil, ensuring uniform root exposure, scalability for large crop areas, and stabilized formulations and optimized dosing are needed for cost‐effective large‐scale use. Moreover, care must be taken to avoid SL‐induced parasitic germination in the soil, which can be addressed by timed applications or integration with crop management practices. Strategies such as slow‐release formulations or carrier‐based delivery may help overcome these barriers.

4.2. Foliar Sprays

Foliar application is the most widely adopted and practical method for field‐scale SL use, offering rapid absorption through stomatal pores and the cuticle. In drought‐stressed wheat, Sedaghat et al. (2017, 2021) demonstrated that 10 μM GR24 foliar sprays significantly enhanced relative moisture content, and antioxidant enzyme activities (POD, CAT, APX), while decreasing electrolyte leakage and malondialdehyde accumulation. Similarly, in Vitis vinifera, foliar treatments with 1–5 μM GR24 improved drought tolerance by elevating chlorophyll content, photosynthetic rate, antioxidant capacity and the expression of VvCCD7, VvCCD8 and VvNCED1 (Min et al. 2019). Under salinity stress, Salvia nemorosa plants treated with 0.1–0.4 μM GR24 sprays exhibited marked improvements in gas exchange parameters, chlorophyll content and essential oil yield, along with reduced oxidative stress indicators (Sharifi and Bidabadi 2020). Similarly, Brassica rapa exposed to low‐temperature stress showed enhanced photosynthesis, antioxidant enzyme activity, and upregulation of MAPK and cold‐regulated genes following 0.05–1.5 μmol L⁻¹ GR24 application (Zhang et al. 2020).

Overall, foliar spraying is an efficient and fast‐acting method for enhancing SL activity under drought, salinity and temperature stresses. Its ability to quickly modulate osmoprotection, membrane stability and redox homeostasis underscores its potential for large‐scale agricultural application. Foliar sprays in field conditions face chemical instability due to sunlight and rainfall, which can be mitigated using encapsulated SL formulations or adjuvants. High costs of synthetic analogues like GR24 may limit large‐scale adoption, highlighting the need for affordable alternatives and optimized application rates. Additionally, ecological risks such as parasitic weed germination can be minimized through targeted application timing, integration with other agronomic practices, and combined root‐and‐foliar strategies to maximize stress tolerance and crop productivity.

4.3. In Vitro and Medium‐Based Applications

In vitro systems using Murashige and Skoog (MS) media offer precise experimental conditions for examining SL signalling at the cellular and molecular levels. T. Yang, Lian, et al. (2020) and Y. Yang, Ren, et al. (2020) found that Malus domestica and Arabidopsis thaliana treated with 5–20 μM GR24 under combined salt, drought and cold stresses exhibited accelerated MdD14 degradation and reduced shoot branching, highlighting SLs' regulatory role in developmental and stress–response networks. Similarly, Helianthus annuus calli cultured on MS medium containing 0.001–0.1 mg L⁻¹ GR24 displayed enhanced biomass, antioxidative enzyme activities and reduced oxidative damage under saline conditions (Zulfiqar et al. 2021). These findings reinforce that in vitro applications are ideal for dissecting the molecular and genetic mechanisms underlying SL‐mediated stress tolerance, providing a valuable complement to whole‐plant studies conducted under natural environments. While in vitro applications provide mechanistic insights, their translation to field conditions faces challenges including SL instability, scalability and cost. Insights from these studies can guide formulation development, controlled‐release strategies and timing of field applications to overcome these limitations.

4.4. Comparative Insights and Practical Implications

Across diverse plant species and stress conditions, GR24 concentrations ranging from 0.1 to 10 μM were generally optimal for achieving positive physiological outcomes. Both suboptimal (≤0.01 μM) and excessive (≥100 μM) concentrations tended to produce inconsistent or inhibitory effects. Among the application strategies, foliar spraying stands out as the most feasible and effective for field implementation, whereas solution‐based and in vitro methods remain essential for mechanistic exploration and controlled experimentation. The method of SL application decisively shapes its physiological efficacy governing processes such as photosynthesis, antioxidant defence, osmotic balance and gene expression modulation. Combining foliar and root‐based application techniques may yield synergistic benefits, providing an integrated strategy to strengthen crop tolerance and productivity under a range of abiotic stresses.

5. Conclusions and Future Perspectives

SLs represent a vital class of signalling molecules that bridge plant development and environmental adaptation. As integrative regulators, SLs orchestrate complex networks of physiological and molecular responses that enhance plant resilience to environmental stresses driven by climate change, including water deficit, soil salinity, extreme temperatures, nutrient shortages and heavy metal contamination. The exogenous treatment of synthetic SL, particularly GR24, has been shown to restore growth, photosynthetic efficiency, osmotic balance and redox homeostasis under adverse environmental conditions. Through modulation of antioxidant defences, hormonal crosstalk and stress‐responsive gene expression, SLs enable plants to maintain metabolic stability and structural integrity during environmental fluctuations. The effectiveness of SL‐mediated stress mitigation is profoundly influenced by the application method and concentration. Foliar spraying has proven to be the most practical and rapid approach under field conditions, whereas solution‐based and in vitro methods provide valuable insights into the underlying signalling pathways and gene‐level regulation. Optimal concentrations typically range between 0.1 and 10 μM, beyond which inconsistent or inhibitory responses may occur. The integration of these approaches offers a promising avenue for improving both physiological performance and stress tolerance across diverse crop species.

Despite substantial progress, much remains to be explored regarding the precise mechanisms through which SLs integrate environmental cues with developmental and metabolic processes. Future investigations need to explore the signalling crosstalk between SLs and additional phytohormones, identifying stress‐specific SL signalling components, and developing more stable, bioavailable analogues suitable for field applications. Moreover, practical strategies for harnessing SLs in crop improvement should be clearly defined. These include genetic engineering of SL biosynthetic or signalling components such as D14, MAX2, or SMXLs to enhance stress resilience while minimizing trade‐offs on shoot branching and yield under normal conditions, and chemical priming using cost‐effective synthetic SL analogues to transiently activate stress responses without permanent genetic modifications. Careful optimization of dosage, timing and tissue‐specific application is crucial to avoid non‐specific responses and developmental penalties. Advances in transcriptomics, metabolomics and nanotechnology may further facilitate the design of targeted SL formulations with enhanced delivery and sustained action. Overall, SLs hold exceptional potential as sustainable bioregulators to reduce the negative effects of climate change on worldwide crop production. By integrating mechanistic insights with these concrete application strategies, SLs can be harnessed to develop resilient, high‐performing crops capable of thriving under increasingly unpredictable environmental conditions.

Conflicts of Interest

The authors declare no conflicts of interest.

El‐Beltagi, H. S. , Gad M., Khedr N., et al. 2026. “Strigolactones as Integrative Regulators of Plant Adaptation and Resilience to Abiotic Stress.” Plant, Cell & Environment 49: 4778–4802. 10.1111/pce.70490.

Data Availability Statement

The data are available on reasonable request.