Effects of humic acid on photosynthetic characteristics and ascorbate-glutathione cycle of melon seedlings under low-temperature stress
Low-temperature stress is a critical factor restricting winter and early spring melon production in China.There are few reports on the effects of Humic acid(HA)on cold tolerance of melon plants.In this experiment,a thick-skinned melon variety'Yugu'was used as the material with water treatment as the control(CK).The study investigated the effects of HA treatment(300 mg/L)on the growth morphology,photosynthetic characteristics,chlorophyll fluorescence parameters,and the Aascorbic Acid-Glutathione(AsA-GSH)cycle,including the impact on antioxidant substances,key enzyme activities,and gene expression levels,under low-temperature stress conditions(10℃/5℃).With the prolonged duration of low-temperature stress,the growth of plants was significantly inhibited.Compared to the control plants,melon seedlings treated with HA exhibited a significant increase in plant height,stem thickness,aboveground and underground fresh weight.Additionally,HA increased the relative content of chlorophyll(SPAD),net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),maximum photochemical efficiency(Fv/Fm),potential photochemical efficiency(Fv/Fo),and non-photochemical quenching coefficient(NPQ).Furthermore,it significantly reduced intercellular CO2 concentration(Ci)and initial fluorescence(Fo).It accelerated the AsA-GSH cycle,significantly reduced the superoxide anion generation rate(O2-·),and malondialdehyde content(MDA)in seedling leaves by increasing the content of reduced ascorbic acid(AsA)and glutathione(GSH),enhancing the activities of ascorbate peroxidase(APX),glutathione reductase(GR),dehydroascorbate reductase(DHAR),and monodehydroascorbate reductase(MDHAR),and upregulating the expression levels of related genes CmAPX,CmGR,CmMDHAR,and CmDHAR,Overall,HA treatment significantly increased the biomass of seedlings under low-temperature stress,effectively improved leaf photosynthetic parameters and chlorophyll fluorescence parameters,and maintained photosystem activity.By optimizing the synthesis of antioxidant substances and key enzyme activities in the AsA-GSH cycle,and upregulating the expression levels of related genes,HA significantly alleviated membrane peroxidation damage in leaves,thereby enhancing the cold resistance of melon seedlings.
Humic acidlow temperature stressmelonphotosynthysisAsAGSH
万方数据
维普
