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ORIGINAL RESEARCH article

Front. Plant Sci.
Sec. Plant Abiotic Stress
Volume 16 - 2025 | doi: 10.3389/fpls.2025.1519950
This article is part of the Research Topic Mechanisms of Stress Tolerance in Horticultural Crops: Physiological and Molecular Insights View all 8 articles

Protective Mechanisms of Exogenous Melatonin on Chlorophyll Metabolism and Photosynthesis in Tomato Seedlings Under Heat Stress

Provisionally accepted
Wangwang An Wangwang An Guangzheng Wang Guangzheng Wang Jianhua Dou Jianhua Dou Yonghai Zhang Yonghai Zhang Qing Yang Qing Yang Yongmei He Yongmei He Zhongqi Tang Zhongqi Tang *Jihua Yu Jihua Yu *
  • College of Horticulture, Gansu Agricultural University, Lanzhou, China

The final, formatted version of the article will be published soon.

    Elevated temperatures severely affect plant growth, reducing yield and quality. Melatonin (MT), a plant biomolecule, is known to enhance stress tolerance, but its role in heat resistance and underlying mechanisms requires further exploration. This study investigates MT's regulatory effects on chlorophyll metabolism and photosynthesis in tomato seedlings under high-temperature stress (40℃). Tomato seedlings treated with 100 μ mol MT showed improved physiological and photosynthetic performance under heat stress. MT application increased osmolytes (proline, soluble sugar), enhanced antioxidant enzyme activities (CAT, POD, APX), and reduced oxidative damage markers (H2O2, O2 -, malondialdehyde, conductivity). Photosynthetic parameters, including key enzyme activities (SBPase, Rubisco, NADP-GAPDH), photochemical efficiency (Fv/Fm, Y(II)), and photochemical quenching (Qp), were significantly improved, restoring the OJIP curve and enhancing photosynthesis. MT also regulated chlorophyll metabolism by promoting synthesis (increasing chlorophyll a and b, ALA, Mg Proto, Pchlide levels) and upregulating synthesis genes (SlHEMA1, SlPORB, SlPORC, SlCHLI) while inhibiting degradation genes (SlCLH1, SlCLH2, SlPAO, SlPPH, SlRCCR). These findings demonstrate that MT enhances tomato heat tolerance by protecting chlorophyll metabolism and photosynthesis, offering a theoretical basis for improving crop resilience to heat stress.

    Keywords: Tomato, Melatonin, high temperature, Photosynthesis, chlorophyll metabolism

    Received: 30 Oct 2024; Accepted: 13 Jan 2025.

    Copyright: © 2025 An, Wang, Dou, Zhang, Yang, He, Tang and Yu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence:
    Zhongqi Tang, College of Horticulture, Gansu Agricultural University, Lanzhou, China
    Jihua Yu, College of Horticulture, Gansu Agricultural University, Lanzhou, China

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