TABLE 2.
A summary of some recent reports on silicon-induced abiotic stress tolerance in crop plants.
| Plant specie | Stress condition | Silicon dose | Protective role | References |
| Salinity | ||||
| Zea mays L. | 80 mM NaCl; 160 mM NaCl | Si (Na2SiO3; 1 mM) | Si addition alleviated the salt toxicity by increasing RWC, MSI, CAT, SOD, APX, and POD activities | Ali et al., 2021 |
| Oryza sativa L. | 200 mM NaCl | 2 mM K2SiO3 | Si improves the rice growth and salinity tolerance by modulating the Salt-Overly Sensitive (SOS) pathway | Gupta et al., 2021 |
| Medicago sativa L. | 120 mM NaCl | Si 3 mM | Si application lowered the oxidative damage, modulated SOD, polyphenol oxidase activities, and improved flavonoid, total polyphenol, and carotenoid contents | El Moukhtari et al., 2021 |
| Solanum tuberosum L. | NaCl 5, 8, and 12 dS m–1 | NaSiO3- NPs 400 mg L–1, SiO2 1000 mg L–1 | Si application increases the proline content and leaf soluble carbohydrates than control Si treatment also lowered the Na+/K+ twice and induced antioxidant enzyme activities |
Kafi et al., 2021 |
| Oryza sativa L. | 0, 25, 50, and 100 mM NaCl | Si, 2 mM | Si application improves the endogenous levels of polyamine by upregulating PAs biosynthetic enzymes While reducing GABA accumulation by downregulating PAs catabolism and maintaining functional GABA shunt, which may lower the oxidative damage |
Das et al., 2021 |
| Cucumis sativus L. | 75 mM NaCl | 1.5 mM Si | Si treatment increases the numerous growth-associated parameters and alleviates the adverse salinity effects. Si application reduces the chlorides (Cl–) shoot concentration | Kaloterakis et al., 2021 |
| Drought | ||||
| Arachis hypogaea L. | Solitary drought (i.e., 10% PEG and 15% PEG) | Na2SiO3 2 mM | Si treatment promotes mineral nutrient absorption improves RWC, leaf chlorophyll content, and biomass It also provides osmoprotection by accumulating metabolites and improving the JA, IAA, GA3, zeatin levels |
Patel et al., 2021 |
| Avena sativa L. | June, only 6 mm rainfall despite a 30-year average of 66.5 mm | Si 3.0 L ha–1 | Si treatment increased the synthesis rate (16.8–149.3%), transpiration (5.4–5.6%), air–leaf temperature difference (16.2–43.2%), Chl (1.0%) and carotenoid (2.5%) content | Kutasy et al., 2022 |
| Zea mays L. | 10% (w/v) PEG | 1.0 mM Na2SiO3 | Si treatment decreased the electrolyte leakage from 0.64 to 0.52% and increased membrane stability 12%, Chl a 35%, Chl b 31%, and carotenoids 51% than control | Bijanzadeh et al., 2022 |
| Zea mays L. | Full irrigation 100% and deficit irrigation 80% | Na2SiO3 0, 2, and 4 mM at 40 and 60 days after planting | Si treatment improves plant growth, gaseous exchange, cell membrane integrity, water use efficiency, physiological performance, and maize productivity It also lowered the concentrations of Ni+2, Cd+2, and Cr+3 in leaves and grains of maize |
El-Mageed et al., 2021 |
| Triticum aestivum L. | Samples drying in an oven at 70°C for 72 h | Si, 6 mM | Si treatment alleviated the oxidative stress and negative drought impacts by increasing the antioxidant enzyme activities | Naz et al., 2021a |
| Cucumis melo L. | soil moisture regimes 100, 75, and 50% FC | H4SiO4, 0, 100, 200, and 400 kg ha–1 | Si treatments increased self-resistance to lodging and strengthened cell wall, restricted fungal disease, and insect infestations, reduced mutual shading, improved water balance, reduced transpiration, and water loss | Alam et al., 2021 |
| Toxic metals/metalloids | ||||
| Triticum aestivum L. | Cd 25 mg kg–1 | 3 mM Si | Si treatment reduced the Cd-mediated oxidative stress and improved photosynthetic pigments, net photosynthetic rate, strengthening the antioxidant defense system, enhancing metabolite accumulation, and improving plant nutrient status | Thind et al., 2020 |
| Triticum aestivum L. | As(V) 25, 50, and 100 μM | 5 mM Si | Si treatment mitigated the arsenate-induced effects and oxidative stress Si application also respiratory cycle, GABA synthesis, and its associated enzymes |
Sil et al., 2018 |
| Capsicum annuum L. | 0.05 mM B, 2.0 mM BT | 2.0 mM Si | Si treatment improves plant growth, proline content, and various antioxidant enzymes activities while lowering the MDA, H2O2 contents, and membrane leakage | Kaya et al., 2020 |
| Poa annua L. | 100 μM Cd | 1 mM Si | Si application alleviated the Cd-toxicity, restored the activity of G6PDH and the expression of G6PDH, and lowered the oxidative stress induced by Cd | Li et al., 2017 |
| Brassica napus L | 0.5 and 1.0 mM CdCl2 | SiO2, 1.0 mM | Si treatment reduced the H2O2 and MDA contents and improved antioxidant defense mechanisms through increasing the AsA and GSH pools and activities of AsA-GSH cycle and glyoxalase system enzymes and CAT | Hasanuzzaman et al., 2017 |
| Zea mays L. | Ni 100 μM | 2.5 mM Si | Si treatment mitigated the Ni-induced stress by enhancing membrane stability and influencing enzymatic (SOD, POX, and CAT) and non-enzymatic (Pro, and AsA) defense systems | Fiala et al., 2021 |
| Salvia officinalis L. | 400 μM Cu | 0, 0.25, 0.5, and 1 mM Si | Si treatment alleviated the oxidative damage, increasing proline content, enhancing the CAT and SOD activities, and up-regulating the SOD gene expression | Pirooz et al., 2021 |
| Temperature (cold/heat) | ||||
| Solanum lycopersicum L. | 30°C to 43 ± 0.5°C | 1 Mm Si | Si application provides thermotolerance by activating the antioxidant system, endogenous phytohormones, and heat shock proteins | Khan et al., 2020b |
| Triticum aestivum L. | 37 ± 2°C | 2 and 4 mM Si | Si application increased the Chl a, b, and a + b and carotenoids by improving the activities of enzymatic antioxidants, CAT, SOD, POD, and osmoprotectants | Mustafa et al., 2021 |
| Triticum aestivum L. | 45°C, 4 h | 1.5 mM K2SiO3 and 1.66 mM Si NPs | Si treatments restored the heat stress-provoked ultrastructural distortions of chloroplasts and the nucleus and enhanced photosynthetic capacity Si treatment also stimulated the overexpression of TaPIP1 and TaNIP2 with an improvement in the RWC |
Younis et al., 2020 |
| Hordeum vulgare L. | 25, 30, and 35°C | 1.5 mM Si | Si application reduced HT-mediated oxidative stress by decreasing the concentration of MDA (39 and 49%) and H2O2 (14 and 56%) and increased shoot (49 and 46%) and root (40 and 34%) dry masses, Chl a (10 and 86%), Chl b (82 and 81%), and carotenoids (53 and 33%) | Hussain et al., 2019 |
| Hordeum vulgare L | 34°C | 0.2, 0.4, and 0.6 mM Na2O3Si.5H2O | Si treatment alleviated the detrimental impacts enhancing the antioxidant enzymes SOD, POD, CAT, and PPO, together with soluble sugars accumulation and free proline for osmotic adjustment | Naz et al., 2021b |
| Euphorbia pulcherrima L. | 40°C | 75 mg L–1 K2SiO3 | Si treatment alleviates the temperature stress by regulating the stomata, photosynthesis, oxidative damage, and by lower production of H2O2 and MDA | Hu et al., 2020 |
| Zea mays L. | 12–14°C | 40 mg H4SiO4 kg–1 | Si treatment related to an improved Zn and Mn status maintains a balanced hormonal (IAA, GA, and CK) status that restores plant growth and helps to increase the expression of enzymatic (SOD and POD) and non-enzymatic (phenolic antioxidants) defense systems | Moradtalab et al., 2018 |
| Hordeum vulgare L. | 5°C and −5°C | 56 mg L–1 as Na2SiO3 | Si treatment increased the activity of antioxidative enzymes and concentrations of soluble carbohydrates and proteins | Joudmand and Hajiboland, 2019 |
| Aloe barbadensis L. | 4°C | Si 500, 1000, 1500, and 2000 mg L–1 | Si treatment improved both enzymatic antioxidant activity and concentrations of soluble sugars | Azarfam et al., 2020 |
| Phyllostachys praecox | 5, 0, and −5°C | Si 0, 0.5, 1.0, 2.0, 4.0, or 8.0 g kg–1 | Si treatment stimulated antioxidant systems and the enzyme activities of SOD, CAT, and POD Whereas the MDA content and cell membrane permeability decreased with all Si treatments |
Qian et al., 2019 |