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<p>Melatonin is of great importance in plant responses to adverse conditions. However, the effects of exogenous melatonin on mitigating salt stress have not been investigated in carrot. In this study, carrot plants were exposed to different concentrations of melatonin (50, 100, 150 µM) under 150 mM NaCl stress. Subsequently, growth parameters, antioxidant enzyme (SOD, POD, CAT) activities, malondialdehyde (MDA) content, and metabolite accumulation (soluble sugars, carotenoids, lignin) were determined, with transcriptome sequencing and histological staining analysis conducted as supplementary assessments. The results showed that salt stress severely inhibited carrot growth, reduced fresh weight, root diameter, and root-shoot ratio, and induced aggravated oxidative damage and excessive lignin deposition. Exogenous melatonin application, particularly at concentrations of 50–100 µM, significantly alleviated salt-induced growth inhibition and physiological damage by enhancing antioxidant enzyme activities, reducing MDA accumulation, and inhibiting excessive lignin biosynthesis. Transcriptome analysis identified key differentially expressed genes involved in lignin biosynthesis and secondary metabolism pathways. In conclusion, melatonin effectively mitigates salt stress in carrots by regulating oxidative defense systems and core metabolic pathways, and low melatonin concentrations exhibit the optimal alleviative effects. These findings clarify the protective mechanisms of melatonin against salinity toxicity and highlight its potential application in improving crop salt tolerance, which provides a theoretical basis for further field verification and agricultural application.</p>

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Melatonin Modulates Antioxidant Properties, Carotenoid Accumulation, and Lignin Deposition to Enhance Adaptability to Salt Stress in Carrot

  • 期刊论文

  • 发表日期：

    2026年6月2日

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  • Guang-Long Wang,
  • Yu-Jie Xu,
  • Wang-Qi Jin,
  • Lin-Yan Jia,
  • Xu-Qin Ren,
  • Ya-Nan Chen,
  • Ai-Sheng Xiong

摘要

Melatonin is of great importance in plant responses to adverse conditions. However, the effects of exogenous melatonin on mitigating salt stress have not been investigated in carrot. In this study, carrot plants were exposed to different concentrations of melatonin (50, 100, 150 µM) under 150 mM NaCl stress. Subsequently, growth parameters, antioxidant enzyme (SOD, POD, CAT) activities, malondialdehyde (MDA) content, and metabolite accumulation (soluble sugars, carotenoids, lignin) were determined, with transcriptome sequencing and histological staining analysis conducted as supplementary assessments. The results showed that salt stress severely inhibited carrot growth, reduced fresh weight, root diameter, and root-shoot ratio, and induced aggravated oxidative damage and excessive lignin deposition. Exogenous melatonin application, particularly at concentrations of 50–100 µM, significantly alleviated salt-induced growth inhibition and physiological damage by enhancing antioxidant enzyme activities, reducing MDA accumulation, and inhibiting excessive lignin biosynthesis. Transcriptome analysis identified key differentially expressed genes involved in lignin biosynthesis and secondary metabolism pathways. In conclusion, melatonin effectively mitigates salt stress in carrots by regulating oxidative defense systems and core metabolic pathways, and low melatonin concentrations exhibit the optimal alleviative effects. These findings clarify the protective mechanisms of melatonin against salinity toxicity and highlight its potential application in improving crop salt tolerance, which provides a theoretical basis for further field verification and agricultural application.