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以玉米第5位全展叶(C4光合叶)为材料,分别测定基部、中部和顶部的光合速率后,将叶片置于强光(2000μmol·m-2·s-1)下处理3h和暗中恢复3h,再测定这3个部位在处理期间的叶绿素荧光参数变化;然后分别从叶片的基部、中部和顶部取样观察显微结构和超微结构,测定叶绿素含量。结果表明,3个部位光合速率和叶绿素含量的大小依次为:中部>顶部>基部。基部的维管束鞘细胞叶绿体数量少,体积小,排列无规律,类囊体膜有部分垛叠;中部和顶部维管束鞘细胞叶绿体数量多,体积大,大部分围绕维管束呈离心排列,类囊体膜垛叠消失。在强光下,基部、中部和顶部均发生光抑制,但光抑制程度不同,根据严重度依次为:基部>顶部>中部,3个部位在暗中的光抑制恢复能力依次为:中部>顶部>基部。与叶基部相比,叶中部在强光下能维持较高的电子传递效率(φEo)和较低的热耗散比率(φDo)。这表明,C4光合循环是保持较高电子传递效率、减轻光抑制的重要因子。
After the photosynthetic rate was measured at the 5th, 4th and 5th leaves of the maize (C4 photosynthetic leaves), the leaves were exposed to light (2000μmol · m-2 · s-1) for 3h and dark After 3h recovery, the chlorophyll fluorescence parameters of these three parts were determined. The microstructure and ultrastructure were sampled from the base, middle and top of the leaves respectively for determination of chlorophyll content. The results showed that the three photosynthetic rate and chlorophyll content in order of size: middle> top> base. At the base, the number of chloroplast in the bundle sheath cells was small, with small volume and irregular arrangement. The thylakoid membrane was partially stacked. The chloroplast in the middle and top vascular bundle sheath cells were numerous and bulky, most of them were arranged in a centrifugal arrangement around the vascular bundle. Capsule stack disappears. Under the bright light, photoinhibition occurred at the base, middle and top, but the degree of photoinhibition was different. According to the severity, the order of photoinhibition recovery of the three parts was: middle> top> middle> Base. Compared with the leaf base, the middle of the leaf can maintain higher electron transfer efficiency (φEo) and lower heat dissipation ratio (φDo) under bright light. This shows that the C4 photosynthetic cycle is to maintain high electron transfer efficiency, reduce light inhibition important factor.