Objective Vegetable peas exhibit high postharvest respiratory metabolism, leading to chlorophyll degradation, texture softening, and nutrient loss. LED light exposure has been proven effective in delaying postharvest senescence and maintaining the quality of fruits and vegetables. This study aims to investigate the synthesis characteristics of melatonin in vegetable peas under LED light conditions and its regulatory effects on senescence indicators, providing a basis for optimizing storage technology.

Method The cultivar 'Zhewan No. 1' was used as the experimental material. Pods free from pests and diseases and with uniform maturity were selected and divided into two groups: the LED light treatment group (40 μmol/m²·s white light) and the dark control group. The samples were stored at room temperature (25±1℃, relative humidity 75%±5%) for 10 d. Samples were taken at 0, 3, and 10 d to measure soluble sugar content, H₂O₂ levels, ·O₂^- levels, weight loss rate, and the expression levels of key enzyme-encoding genes involved in ethylene synthesis, which are indicators of quality and senescence. Melatonin content was determined, and the expression of melatonin synthesis genes (PsSNAT and PsCOMT) were analyzed. Following the application of exogenous melatonin, quality and senescence indicators were measured.

Result Compared to the dark control group, the LED treatment significantly increased the soluble sugar content in vegetable peas during the 10 d storage at room temperature (25±1℃), inhibited the accumulation of H₂O₂ and ·O₂^-, and suppressed the expression of key enzyme-encoding genes involved in ethylene synthesis. The weight loss rate of the LED-treated group decreased to 12.3% (vs. 15.9% in the control group). Additionally, LED light significantly promoted melatonin accumulation, with a content of 10.47 ng/g at 10 d—twice as high as that in the control group. Concurrently, the expression levels of PsSNAT and PsCOMT were significantly upregulated, and both gene promoters contain E-Box light-responsive elements. Furthermore, exogenous melatonin application inhibited reactive oxygen species accumulation and the expression of ethylene synthesis-related key enzyme genes, maintained soluble sugar content, and reduced weight loss rate. These results indicate that melatonin can delay the postharvest senescence of vegetable pea.

Conclusion The application of LED light can promote melatonin accumulation by upregulating the expression of PsCOMT and PsSNAT genes, thereby inhibiting the accumulation of reactive oxygen species and delaying postharvest senescence of vegetable peas. This provides theoretical support for green and low-energy storage solutions.