小麦旗叶衰老期间光合作用与叶肉细胞超微结构变化

Changes of Photosynthesis and Ultrastructure of Mesophyll CellsDuring Senescence in Wheat Flag Leaves

小麦开花后衰老期间旗叶光合作用速率变化分缓慢下降和快速下降两个阶段。光合作用缓降期间（开花至花后２５ｄ）叶片可溶性蛋白质含量先平稳变化（开花至花后１０ｄ），之后持续降低；叶片叶绿素含量由缓慢升高（开花至花后８ｄ）转为缓慢下降；叶肉细胞结构保持完整。光合作用速降期间（开花２６ｄ以后）旗叶光合作用速率、可溶性蛋白质含量和叶绿素含量快速平行下降，叶绿体嗜锇颗粒数量和体积均增加，基粒片层和基质片层肿胀并分成囊泡，叶绿体被膜破裂，基质散逸于细胞内。

The change of photosynthesis could be divided into slow-fall phase and sharp-fall phase during senescence of flag leaves after anthesis in winte wheat (Triticum aestivum L. cv Lumai 215953). During slow-fall phase of photosynthesis (from anthesis to 25 days after), the content of leaf soluble protein remained fairly constant at the first 10 days after anthesis and then declined gradually. And the leaf chorophyll increased slightly ( from anthesis to 8 days after) then decreased slowly. The ultrastructure of chloroplast was intact. In sharp-fall phase, photosynthetic rate, content of soluble protein as well as content of chlorophyll dropped sharply in parallel, and the ultrastructure chloroplast changed markedly. Osmiophilic globuli increased in size and number, grana and inter grana lamellae became distended and later dissociated into distinct vesicles. Finally, the chloroplast envelope ruptured and plastid contents dispersed throughout the cell interior.