荔枝雌蕊发育过程中钙分布变化与细胞程序性死亡

应用焦锑酸钾沉淀法研究了荔枝雌花和雄花雌蕊发育过程中钙的分布变化。在大孢子母细胞阶段，雌花近珠孔内珠被细胞和花柱细胞的钙沉淀颗粒主要分布在细胞壁和细胞间隙，少部分在液泡；雌花花柱维管细胞中含有很多的钙沉淀颗粒；在雄花的近珠孔内珠被细胞钙沉淀颗粒大多在液泡中；雄花花柱细胞和维管细胞中钙沉淀颗粒很少。大孢子母细胞减数分裂后，雌花雌蕊继续发育，雄花雌蕊败育。雌花维管中的钙沉淀颗粒数量减少，可能被转运到将要发生花粉萌发和受精的部位。雌花近珠孔内珠被细胞壁的钙沉淀颗粒分布增加，花柱细胞从上（近柱头）到下（近子房）钙沉淀颗粒量递增。雄花近珠孔内珠被细胞发生程序性死亡：液泡中的钙进入细胞核启动细胞程序性死亡，核周隙与质膜腔形成连续的通道，钙在核与细胞质之间的流动不受限制；在特定的时间段，钙沉淀颗粒出现在线粒体、过氧化物体和线型内质网的外膜上。钙在细胞中重新分布可能触发和调节细胞程序性死亡的进程。缺乏钙沉淀颗粒的雄花花柱细胞迅速解体。

Distribution Changes of Calcium and Programmed Cell Death in the Pistil of Litchi (Litchi chinensis Sonn.) Flower during Its Development

Potassium pyroantimonate precipitationmethod was used for investigating calcium distributionand cell ultrastructure change during development of pis-tils of litchi male and female flower. The results showedthat at the megasporocyte stage of female flowers, cal-cium precipitates was located mainly at cell wall and in-tercellular space of inner integument near the micropyleand style cells, and to a lesser extent in vacuoles. Vascu-lar tissues also contained much calcium precipitates. Ininner integument cells near the micropyle of male flowers,the vacuole contained most of the calcium precipitates.Calcium precipitates in style cell and vascular tissues ofmale flowers was sparse and seldom seen. After meiosisof megasporocyte, pistils of female flowers continued togrow and those of male flowers aborted. In femaleflowers, calcium precipitates concentration became lowerand calcium precipitates was probably transported to theplaces for future pollen bourgeoning and fertilization.Cell wall calcium precipitates concentration increasedin the inner integument cells near the micropyle. Cal-cium precipitates concentration increased from topperstyle cells to lower ones. In male flowers, inner integu-ment cells near the micropyle underwent the programmedcell death (PCD): flow of calcium from vacuoles intonucleus might had triggered the PCD process. A con-tinuous channel was formed between perinuclear spaceand cytoplasm membrane lumen, and calcium flowedfreely between nuclear membrane and plasma membrane.At certain time and locations, calcium precipitates wasnewly appeared at some organelles like endoplasimicreticulum, mitochondria and peroxisomes. This calciumredistribution in cells might trigger and regulate the pro-cess of PCD. In male flowers, style cells containing nocalcium precipitation soon began to degenerate.