Alleviating effects of exogenous melatonin on leaf senescence of muskmelon after fruit setting

ZHENG Haiqiang; LIU Mengze; LIU Haihe; ZHANG Yanping; CAO Yanxia; ZHU Libao

doi:10.16861/j.cnki.zggc.2025.0232

Abstract：To investigate the effects of exogenous melatonin on leaf senescence in muskmelon,the variety Nongda 103 was used as the test material.During the flowering period of female flowers in spring greenhouse conditions,exogenous melatonin solutions of 100,200,300,and 400 μmol·L-1 were sprayed on the leaves,with distilled water as the control.Physiological indicators of chlorophyll,reactive oxygen species metabolism,and nitrogen metabolism in leaves at the fruiting node were compared and analyzed.The results showed that from 14 to 35 days after the first treatment,compared with the control,the 200 μmol·L-1 melatonin treatment significantly increased the chlorophyll content by 37.21％-77.36％,the chlorophyll fluorescence value Fv/Fm and ETR by 11.97％-18.36％and 38.41％-44.63％,the activities of antioxidant enzymes SOD,POD,and CAT by 12.54％-29.30％,18.28％-38.92％,and 67.05％-207.69％,the activities of nitrogen metabolism enzymes NR and GS by 20.63％-60.00％and 6.34％-11.84％,respectively,while the O2-·production rate was significantly reduced by 34.75％-47.81％.In conclusion,exogenous melatonin can enhance antioxidant enzyme activity,accelerate reactive oxygen species scavening,thereby delaying leaf senescence,and further improve leaf photosynthetic performance and nitrogen metabolism capacity,promoting plant growth.Under the conditions of this experiment,the 200 μmol·L-1 melatonin treatment showed the best effect in delaying early leaf senescence.