外源NO对NaHCO3胁迫下黑麦草幼苗光合生理响应的调节

采用营养液砂培方法,研究了外源一氧化氮(NO)对100 mmol/L NaHCO3胁迫下黑麦草幼苗叶片叶绿素含量、光合气体交换和叶绿素荧光参数、光能分配及叶黄素循环的影响。结果表明:(1)外施60μmol/L NO供体硝普钠(SNP)显著缓解了NaHCO3胁迫下叶绿素含量、净光合速率(Pn)、气孔导度(Gs)和气孔限制值(Ls)的下降及胞间CO2浓度(Ci)的升高,提高了光系统Ⅱ(PSⅡ)的潜在活性(Fv/Fo)、最大光化学效率(Fv/Fm)、实际光化学效率(ΦPSⅡ)和光化学猝灭(qP),降低了初始荧光(Fo)和非光化学猝灭(NPQ)。(2)NaHCO3胁迫下,外施SNP显著抑制了天线转换效率(Fv’/Fm’)的下降,降低了光系统间激发能分配的不平衡性(β/α-1)和天线热耗散的比例(D),提高了吸收光能中用于光化学反应的比例(P),而对PSⅡ反应中心的过剩光能(Ex)无明显影响。(3)外施SNP显著降低了NaHCO3胁迫下叶黄素循环库(V+A+Z)下降和叶黄素循环脱环氧化状态(A+Z)/(V+A+Z)上升的幅度。但SNP对NaHCO3胁迫的缓解效应可被NO清除剂血红蛋白(Hb)部分或完全地逆转,SNP的分解产物NaNO2处理对NaHCO3胁迫无明显改善。表明外源NO可能通过提高光化学效率,缓解了碱胁迫引起的光抑制对光合机构的破坏,从而提高黑麦草的光合效率。

Regulation of exogenous nitric oxide on photosynthetic physiological response of Lolium perenne seedlings under NaHCO3 Stress

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.