Exogenous melatonin enhances drought tolerance and germination in common buckwheat seeds through the coordinated effects of antioxidant and osmotic regulation

Abstract

Background

Drought stress is a major constraint on seed germination and crop productivity, particularly for drought-sensitive crops like common buckwheat (Fagopyrum esculentum). Exogenous melatonin has emerged as a promising strategy to mitigate drought stress by enhancing plant physiological and biochemical responses. However, its specific roles in regulating antioxidant defenses, osmotic adjustment, and plant compounds biosynthesis during buckwheat seed germination under drought stress remain poorly understood.

Results

This study investigated the effects of 200 µM exogenous melatonin on common buckwheat germination under polyethylene glycol (PEG-6000)-induced drought stress. Melatonin significantly improved germination rates and radicle growth, reduced membrane damage, and enhanced osmotic regulation by increasing proline, soluble sugars, and proteins. Antioxidant enzyme activities (catalase, peroxidase, and superoxide dismutase) and associated gene expression (FtCAT, FtPOD, FtSOD) were markedly upregulated. Molecular docking and dynamics simulations revealed a stable interaction between rutin, a secondary metabolite, and catalase, suggesting enhanced enzyme stabilization. Additionally, melatonin increased rutin and methyl jasmonate synthesis, which contributed to antioxidant defenses and reduced oxidative damage. The coordinated effects of melatonin improved drought tolerance in buckwheat seeds by optimizing osmotic balance, strengthening antioxidant capacity, and stabilizing cellular structures.

Conclusions

Exogenous melatonin enhances drought tolerance in common buckwheat seeds through the coordinated regulation of antioxidant defenses, osmotic adjustment, and plant compounds production, including methyl jasmonate and rutin, during germination. These findings offer valuable insights for developing practical strategies to improve drought resilience and crop establishment in sensitive agricultural species under water-limited conditions.