外源NO对NaHCO3胁迫下黑麦草幼苗光合生理响应的调节

Abstract

As an important signaling molecule,Nitric oxide(NO) involved in the responses regulation of various abiotic stresses including drought,salt and heavy metal and so on in plants.Scientific study revealed that NO could alleviate the decrease of photosynthetic rate and the damage of photosynthesis system in plants under abiotic stresses.However,whether NO improve the photosynthetic ability by means of regulating of light-energy utilization in ryegrass(Lolium perenne L.) seedlings under alkaline stress is still not yet understood.The study was conducted in sandy nutrient solution to investigate the effects of exogenous NO on the chlorophyll content,photosynthetic gas exchange and chlorophyll fluorescence parameters,light energy allocation as well as xanthophyll cycle in leaves of ryegrass seedlings under 100 mmol/L NaHCO3 stress.The results show that:(1) 60 μmol/L exogenous NO donor sodium nitroprusside(SNP) significantly alleviated the decreases of the chlorophyll content,net photosynthetic rate(Pn),stomatal conductance(Gs) and stomatal limited value(Ls) and the increase of intercellular CO2 concentration(Ci) in ryegrass seedling leaves caused by NaHCO3 stress;and increased the potential activity(Fv/Fo),maximum photochemical efficiency(Fv/Fm),actual photochemical efficiency(ΦPSⅡ) and photochemical quenching(qP),but decreased the initial fluorescence(Fo) and non-photochemical quenching(NPQ) of photosystem Ⅱ(PSⅡ) in the seedling leaves under NaHCO3 stress.(2) Under the stress,applying SNP significantly inhibited the decrease of antenna efficiency at open centers in the presence of NPQ(Fv′/Fm′),decreased the deviation from full balance between PSI and PSⅡ(β/α-1) and the proportion allocated in antenna heat dissipation(D),and increased the absorbed light energy allocated to the photochemical reaction of PSⅡ(P),but no effect on the PSⅡ excessive energy(Ex).(3) Applying SNP significantly inhibited the decrease of xanthophyll cycle pool(V+A+Z),and the increase of the de-epoxidation extent of xanthophyll cycle(A+Z) /(V+A+Z) caused by the stress in ryegrass seedling leaves.The addition of hemoglobin(Hb),a NO scavenger,eliminated partly or completely the effects of SNP,while applying NaNO2(the decomposition products of SNP) had no significant alleviation effects on NaHCO3 stress.These results suggested that exogenous NO may alleviate the damage of photoinhibition caused by alkaline stress to the leaf photosynthetic apparatus via increasing the photochemical efficiency,thus improve photosynthetic efficiency of the ryegrass plants under alkaline stress.