大气CO2倍增条件下冬小麦气体交换对高温干旱及复水过程的响应

Responses of leaf gas exchange to high temperature and drought combination as well as re-watering of winter wheat under doubling atmospheric CO2 concentration

探究大气CO2浓度倍增条件下冬小麦气体交换参数对高温干旱及复水过程的生理响应机制,有助于提高生态过程模型的模拟精度,更加准确地预测全球气候变化对农田生态系统初级生产力及其生态服务功能的影响。利用4个可精准控制CO2浓度和温度的大型人工气候室,研究了CO2浓度倍增条件下高温干旱及复水过程对冬小麦气孔特征和气体交换参数的影响。结果表明,CO2浓度倍增(E)导致冬小麦远轴面气孔密度增加、气孔宽度减小、气孔空间分布规则程度降低,但提高叶片的净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和水分利用效率(WUE)。高温干旱(HD)使叶片气孔长度、密度、周长和面积减小,导致叶片气体交换参数均显著下降。然而,高CO2浓度及高温干旱(EHD)导致气体交换参数下降幅度相对较小,表明高CO2浓度对高温干旱具有一定的缓解作用。此外,干旱复水后,不同处理条件下冬小麦叶片气体交换参数均有所升高,但高温干旱下叶片的气体交换参数仍未能恢复到对照水平,暗示光合器官可能在高温干旱时遭到损伤和破坏。

Understanding the responsible mechanisms of crops to combined environmental stresses such as elevated CO2 concentration,climate warming,and drought is critical to improve the accuracy of ecological process models,and thus accurately predict the impacts of global climate change on the Net Primary Production(NPP)and ecosystem service function of farmlands.Four environmental growth chambers accurately controlling CO2 concentration and temperature were employed to investigate the combined effects of high temperature and drought stresses on the stomatal traits and leaf gas exchange during re-watering under doubling CO2 concentration.We found that elevated CO2 concentration(E)increased the stomatal density,decreased the stomatal width and made the spatial distribution pattern of stomata irregular on the abaxial leaf surface,while enhanced the net photosynthetic rates(Pn),stomatal conductance(Gs),transpiration rates(Tr),and water use efficiency(WUE).The stomatal length,width,perimeter and area were substantially decreased under the combined high temperature and drought stress(HD),resulting in dramatic decline of leaf gas exchange parameters.Doubling CO2 concentration made the leaf gas exchange parameters enhanced under the HD treatment,suggesting that elevated CO2 concentration can compensate the negative impacts of heat and drought on the physiological processes of winter wheat.Additionally,the leaf gas exchange of winter wheat subjected to the high temperature and drought stresses was enhanced after re-watering,but these parameters were still lower than those of Control,suggesting that the photosynthetic apparatus may be damaged by the combined high temperature and drought stresses.