Melatonin Improves Salt Tolerance in Tomato Seedlings by Enhancing Photosystem II Functionality and Calvin Cycle Activity

作者：Xianjun Chen, Bi Chen, Yao Jiang, Jianwei Zhang, Mingjie Liu, Qin Yang, Huiying Liu · 发表于：Plants · 年份：2025 · DOI：10.3390/plants14121785 · 被引用次数：7 · 研究领域：Light effects on plants、Plant Molecular Biology Research、Photosynthetic Processes and Mechanisms

Salt stress severely impairs photosynthesis and development in tomato seedlings. This study investigated the regulatory role of exogenous melatonin (MT) on photosynthetic performance under salt stress by determining chlorophyll content, chlorophyll a fluorescence parameters, Calvin cycle enzyme activities, and related gene expression. Results showed that salt stress significantly reduced chlorophyll content and impaired photosystem II (PSII) functionality, as evidenced by the increased minimum fluorescence (Fo) and decreased maximum quantum efficiency of PSII (Fv/Fm) and effective PSII quantum yield (ΦPSII). MT application mitigated these negative effects, as reflected by higher Fv/Fm, increased chlorophyll content, and lower non-photochemical quenching (NPQ). In addition, MT-treated plants exhibited improved PSII electron transport and more efficient use of absorbed light energy, as shown by elevated ΦPSII and qP values. These changes suggest improved PSII functional stability and reduced excess thermal energy dissipation. Furthermore, MT significantly enhanced both the activity and expression of key enzymes involved in the Calvin cycle, including ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), Rubisco activase (RCA), phosphoglycerate kinase (PGK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), fructose-1,6-bisphosphatase (FBPase), fructose-bisphosphate aldolase (FBA), transketolase (TK), and sedoheptulose-1,7-bisphosphatase (SBPase), thereby promoting carbon f...