香榧小孢子叶球的发育及花粉超微结构研究

香榧Torreya grondis Foft.ex Lindl.小孢子叶球发生于当年生新枝的叶腋内,8月末出现小孢子叶突起,9月形成小孢子囊,10月到第二年的3月初小孢子母细胞大量形成,3月中旬,小孢子母细胞减数分裂,4月上旬是单核花粉期,4月中旬是二核花粉期。在花粉的发育过程中不形成原叶体细胞。 不良的温度影响花粉的正常发育,从而形成大量的败育花粉。败育花粉通常比正常花粉要小一些,充满淀粉粒,花粉壁薄,细胞中线粒体、内质网少,线粒体嵴发育不良,核质浓缩成几团,生理活性低,糖的代谢受阻。此外,还见到一些膜状溶酶体,使花粉中的原生质体发生自溶。

Studies on the Development of Male Cone and the Ultrastructure of Pollen in Torreya grandis

The young staminate strobilus in Torreya grandis Fort.ex Lindl. emerge in the leaf axil of the new twigs that arise in the same year. The micro-sporophyll appears in August, and the microsporangium in September. The period of large production of microspore mother cells are from October to March of the following year.In mid-March,the meiosis of microspore mother cells takes place, which lasts for two weeks or so. The uninucleate pollen stage comes forth in early April, and the binucleate pollen stage in mid-April. No vegetative cell is formed during the course of the pollen development. The pollen development is often affected by environmental factors and is particularly influenced by temperature change in the course of its development. The unsuitable temperature affects the normal development of pollen, which leads to the formation of a large quantity of under-developed pollen grains. The under-developed pollen grain is usually smaller than the normal pollen grain and has a thinner wall. It is full of starch grains, a few mitochondria and endoplasmic reticula. Their mitochondrial cristae are underdeveloped, and their nucleoplasm is concentrated into several clumps. The above-mentioned features indicate a lower physiological activity of the underdeveloped pollen which hinders hydrate metabolism. In addition, several membranous lysosomes are observed in the under-developed pollen. Their existence may cause autolysis of the protoplasm, one of the reasons for the under-development of pollen.