Table 1.
Examples of direct and indirect hormonal effects on photosynthesis and photoprotection in plants exposed to drought or high light stress described during the last 5 years
| Hormone | Species | Stress | Plant material | Treatment | Effects | Reference |
|---|---|---|---|---|---|---|
| ABA | Lycium chinense | Drought | 15-week-old plants with 35–40 leaves | 15% soil moisture level for 4 weeks | ABA modulates NPQ and ϕPSII through the regulation of VDE expression | Guan et al. (2015) |
| ABA | Arabidopsis thaliana | High light | 18–21-d-old wild type and mutants (Ler, aba1, abi1, abi4-102, gun1-9) | 1,000 µmol m−2 s−1 high light for (i) 0, 20, and 60 s; (ii) 0, 10, 60, and 300 s | 20% of transcript accumulation in plants responds to ABA in an ultra-fast response within seconds | Suzuki et al. (2015) |
| ABA | Arabidopsis thaliana | High light | 30–45-d-old wild type and mutants (Ler, rbohD, aba1-1 aba2-1; aba3-1, slac1, lox1, abi1-1, ghr1) | 2000 µmol m−2 s−1 high light (0, 1, 5, and 10 min) on a circular area (0.75 cm in diameter) at the tip of a mature leaf | ABA is involved in local and systemic signaling, regulates stomatal closure in local leaves, and is required for H2O2 and SA accumulation in local and systemic leaves | Devireddy et al. (2018) |
| ABA | Spring barley cvs. “Sebastian” | Drought | 4-d-old seedlings | Liquid MS medium with 200 µM ABA for 2 d; on day 15 severe drought stress application with 1.5% volumetric water content for 10 d | High-dose ABA application negatively affects the electron fate between photosynthetic antenna absorption and QA at the acceptor side of PSII | Daszkowska-Golec et al. (2019) |
| ABA | Arabidopsis thaliana | High light | 4-d-old wild type and mutants (NCED and pifq) | 1,200 µmol m−2 s−1 high light for 72 h | ABA regulates middle- and long-term high-light response; upregulation of ABA biosynthetic genes (NCED3, NCED5, and NCED9 within 0.5 h and NCED2 within 24 h); induction of NCED3/5 by high light was independent of PIFs | Huang et al. (2019) |
| Auxin | Arabidopsis thaliana | High light | 4-d-old seedlings | 1,200 µmol m−2 s−1 high light for 72 h | Auxin biosynthesis is repressed after long-term high light exposure | Huang et al. (2019) |
| Auxin | Clover | Drought | Seedlings at the two-leaf stage | 1 µM IAA about 7 d; 15% PEG-6000 for 14 d. | Exogenous IAA enhanced chlorophyll content accompanied with increased ABA and JA contents | Zhang et al. (2020) |
| BRs | Cowpea | Drought | 6-d-old seedlings | Semi-hydroponic conditions: 100 nM EBR spayed at 6-d interval until day 18; water deficit: days 18–20 solution was removed completely | BRs increased ϕPSII, qP, and ETR, antioxidant enzymes (SOD, CAT, APX, and POX) and total chlorophyll contents | Lima and Lobato (2017) |
| BRs | Maize | Drought | 30-d-old seedlings (drought-sensitive 2023 and drought-tolerant CE704) with three fully developed leaves | Cessation of watering for 14 d and final 3% soil water content. | Three-fold higher BRs (especially typhasterol and 28-norbrassinolide) contents in drought-tolerant genotype accompanied with higher chlorophyll and carotenoids contents compared with drought-sensitive genotype | Tůmová et al. (2018) |
| BRs | Arabidopsis thaliana | High light | 4-d-old seedlings | 1,200 µmol m−2 s−1 high light for 72 h | Biosynthesis genes were down regulated, suggesting a negative role | Huang et al. (2019) |
| CKs | Arabidopsis thaliana | High light | 5-d-old wild type and mutants (ahk2ahk3, ahk4, and ahk3ahk4) | 400 µmol m−2 s−1 light (8-h light/16-h dark) for 6 d on detached leaves | Mutants with insufficient CK signaling showed better PSII function than wild-type plants | Janečková et al. (2018) |
| CKs | Arabidopsis thaliana | High light | 4-d-old seedlings | 1,200 µmol m−2 s−1 high light for 72 h | CK biosynthesis was repressed after long-term high light exposure | Huang et al. (2019) |
| Ethylene | Arabidopsis thaliana | High light | 3-week-old wild type and mutants (eto1-1 and crt1-3) | 1,300 and 1900 PFD high light | Ethylene repressed the expression and activation of VDE and increased ROS | Chen and Gallie (2015) |
| JAs | Arabidopsis thaliana | High light |
5–8-week-old wild type and oxi1 null mutants deficient in the OXI1 kinase |
1,500 µmol m−2 s−1 PFD, 7°C/14°C day/night temperature, and 380 ppm CO2 for 26 h |
oxi mutants showed a down-regulation of the JA pathway genes in leaves, suggesting a link between OXI1 protein and JAs in PCD under high light stress; OPDA appeared to antagonize PCD, while JA and JA-Ile promoted 1O2-induced PCD | Shumbe et al. (2016) |
| JAs | Arabidopsis thaliana | High light | 30–45-d-old wild type and mutants (Ler, rbohD, aba1-1 aba2-1; aba3-1, slac1, lox1, abi1-1, ghr1) | 2,000 µmol m−2 s−1 high light (0, 1, 5, and 10 min) on a circular area (0.75 cm in diameter) at the tip of a mature leaf | JAs were involved in systemic signaling (stomatal closure of systemic leaves) | Devireddy et al. (2018) |
| JAs | Arabidopsis thaliana | High light | 30-d-old wild type and mutants (aos, sid2) | 650 µmol m−2 s−1 light + 42°C for 7 h | JAs regulated unique transcriptional responses under combined high light and heat stress and promoted APX1 and APX2 expression | Balfagón et al. (2019) |
| JAs | Arabidopsis thaliana | High light | 4-d-old seedlings | 1,200 µmol m−2 s−1 high light for 72 h | Upregulation of JA biosynthetic genes during long-term high-light treatment | Huang et al. (2019) |
| SA | Wheat | Drought | 45-d-old seedlings | 0.5 mM SA application with 15 d intervals from day 45 till harvesting; water stress levels were maintained based on RWC (50% and 75%) | SA increased Rubisco abundance, Rubisco activators, Rubp regenerating enzymes, SBPase, FBPase, OEE1, OEE2, FNR, Chla/bBP, TLP, and ATP synthase | Sharma et al. (2017) |
| SA | Soybean | Drought | 45-d-old seedlings | Seed priming (0.5 mM SA solution for 6 h); water stress levels were maintained based on RWC of leaf (50% and 75%) | SA increased Rubisco, Rubisco activase, Chla/bBP, OEE1, OEE2, FNR, Chla/bBP, PSII stability proteins, and antioxidant enzymes (SOD, APX, GR, CAT) | Sharma et al. (2018) |
ATP, adenosine triphosphate; Chla/bBP, chlorophyll a/b binding protein; EBR, 24-epibrassinolide; FBPase, fructose-1,6-bisphosphatase; IAA, índole-3-acetic acid; JA-Ile, jasmonoyl-isoleucine; MS, Murashige and Skoog; NCED, 9-cis-epoxycarotenoid dioxygenase; OEE, oxygen evolving enhancer protein; OXI1, OXIDATIVE SIGNA-INDUCIBLE1; PIFs, phytochrome interacting factors; PN, net photosynthesis rate; qP, photochemical quenching; ϕPSII, quantum yield of PSII; RWC, relative leaf wáter content; Rubisco, ribulose-1,5-bisphosphate carboxylase oxygenase; Rubp, ribulose-1,5-bisphosphate; SBPase, sedoheptulose-1,7-bisphosphatase; TLP, thaumatin like protein.