水分胁迫导致小麦叶片光合作用下降的非气孔因素

小麦幼苗根部在不同渗透势溶液(PEG4000)中经受不同时间胁迫,叶片的RWC和水势下降、膜的RP、R_s和C_i升高。同时P_n下降。它还使叶肉细胞内的叶绿体排列发生紊乱、膜受到破坏、基粒间的连接松驰或消失、类囊体片层肿胀和解体、脂质小球增多和淀粉粒消失。相应地叶片的RuBPC活性下降和GO活性升高,从而促进了C_i的累积。此外MDA含量增多是自由基诱发脂质过氧化的结果。这些非气孔因素可能是造成小麦光合作用下降的重要原因。

Non-stomatal Factors Causing Photosynthetic Rate Decline Induced by Water Stress

When roots of wheat seedlings were subjected to water stress bytreating with PEG (MW 4000) solutions with different osmotic potentials for different durations, relative water content and water potential decreased. As a result, relative permeability of membrances, stomatal resistances and intercellular CO_2 concentlation in leaves increased, while net photosynthetic (?)ate decreased. This can be explained by the disorder in chloroplast in mesophyll cells, the damage of cell membrane, the loosening of linkage between grana and the disruption of thylakoid lamellae. At the same time, the activity of glycolate oxidase increased, and that of RuBPCase activity decreased significantly, which could explain the accumulation of CO_2 in intercellular space. The rise of malondialdehyde content and the damage of membranes can be the result of lipid peroxidation by induced free radical, which mav be one of the most important factors causing the reduction of photosynthetic rate. The changes of photosynthetic apparatus under water stress and their interactions are very complex, and deeper study is needed to single out the most important factor.