Journal
PLANT PHYSIOLOGY AND BIOCHEMISTRY
Volume 167, Issue -, Pages 309-320Publisher
ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
DOI: 10.1016/j.plaphy.2021.08.002
Keywords
Melatonin; High temperature; Photosynthesis; Photosystem I and II; CO2 assimilation; Tomato
Categories
Funding
- National Natural Science Foundation of China [32072649]
- China Earmarked Fund for Modern Agro-industry Technology Research System [CARS-23-B12]
- Jiangsu Province Scientific and Technological Achievements into Special Fund [BE2017701]
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Melatonin treatment enhanced photosynthetic efficiency in tomato seedlings under high-temperature stress by increasing endogenous melatonin levels and photosynthetic pigment content, upregulating biosynthesis gene expression, and boosting CO2 assimilation and electron transport efficiency.
Photosynthesis is a fundamental biosynthetic process in plants that can enhance carbon absorption and increase crop productivity. Heat stress severely inhibits photosynthetic efficiency. Melatonin is a bio-stimulator capable of regulating diverse abiotic stress tolerances. However, the underlying mechanisms of melatonin-mediated photosynthesis in plants exposed to heat stress largely remain elucidated. Our results revealed that melatonin treatment (100 mu M) in tomato seedlings increased the endogenous melatonin levels and photosynthetic pigment content along with upregulated of their biosynthesis gene expression under high-temperature stress (42 degrees C for 24 h), whereas heat stress significantly decreased the values of gas exchange parameters. Under heat stress, melatonin boosted CO2 assimilation, i.e., V-c,V- max (maximum rate of ribulose-1,5-bisphosphate carboxylase, Rubisco), and J(max) (electron transport of Rubisco generation) and also enhanced the Rubisco and FBPase activities, which resulted in upregulated photosynthetic related gene expression. In addition, heat stress greatly reduced the photochemical chemistry of photosystem II (PSII) and photosystem I (PSI), particularly the maximum quantum efficiency of PSII (Fv/Fm) and PSI (Pm). Conversely, melatonin supplementation increased the chlorophyll a fluorescence parameters led to amplifying the electron transport efficiency. Moreover, heat stress decreased the actual PSII efficiency (Phi PSII), electron transport rate (ETR) and photochemical quenching coefficient (qP), while increasing nonphotochemical quenching (NPQ); however, melatonin reversed these values, which helps to fostering the dissipation of excess excitation energy. Taken together, our results provide a concrete insight into the efficacy of melatonin-mediated photosynthesis performance in a high-temperature regime.
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