玉米叶片原形成层细胞衰退过程的超微结构研究

Ultrastructural Study on the Degenerative Processes of Procambial Cells in Maize Leaf Blades 

在玉米（ＺｅａｍａｙｓＬ．）叶片原形成层发育的不同阶段常出现细胞衰退的现象，其衰退方式可分为自溶型和凝缩型。自溶型衰退的特点是细胞发生一系列降解活动最后导致细胞自溶死亡。衰退早期的细胞出现明显的自体吞噬活动，伴随核糖体和细胞质电子密度下降。衰退最后阶段的细胞自溶导致所有原生质组分的解体和消失，其中细胞核和质膜是最后消失的组分。凝缩型衰退的起动则伴随细胞质密度的增大。随着衰退的进行，原生质组分以一定顺序逐步退化解体：首先是高尔基体和内质网，接着是质体、细胞核和部分线粒体。但到衰退后期当细胞被挤压塌陷时仍有质膜、核糖体和线粒体存在。

Cell degeneration often occurred in Zea mays L. leaf procambium in various stages of development and could be classified either in the form of autolysis or condensation. In the autolytic degeneration the cells underwent a series of events from the appearance of prominant autophagie activity in the early stages, accompanied by a decrease of ribosomes and electron density of cytoplasm to the final stages of autolysis resulting in disorganization and disappearance of all protoplasmic components, of which the nuclei and plasmalemma were the last to disappear. In the condensed type the initiation of cell degeneration was accompanied by an increase in the cytoplasmic density. As cell degeneration progressed, the protoplasmic components appeared to disintegrate and disappear in an orderly fashion i.e. dictyosomes and ER disorganized first, followed by plastids, nuclei and some mitochondria. The plasmalemma, ribosomes and mitochondria were still recognizable as the cell being crushed by the surrounding cells during the final stages of degeneration.