摘要
应用电子显微镜观察了春兰(Cymbidium goeringii)成熟时期花粉块中不同部位四合花粉壁的结构,同时用不同的组织化学方法对壁的成分进行了测试。花粉块中所有的四合花粉的花粉壁都可以区分外壁和内壁,但因所处的部位不同,外壁的结构有很大的变异。花粉块表面的四合花粉,与绒毡层相邻的花粉壁(外向壁)具覆盖层和颗粒状层的外壁外层和外壁内层,无基足层以及存在一般的纤维素内壁。处于四合花粉之间的花粉外向壁和四合花粉内花粉之间的壁(内向壁),外壁外层结构简化,孢粉素沉积降低。位于花粉块外围的数层四合花粉其外壁外层退化的程度由外至里增加,而内部的四合花粉缺少外壁外层。本研究还说明花粉粘合成花粉块的机理是基于下列特征的综合效果:(1)在一个四合花粉中的花粉之间,由内壁形成的桥,(2)在一个四合花粉中的花粉之间形成胞质通道,(3)四合花粉内形成不完全的细胞壁,(4)成熟花粉的体积很小和排列紧密和(5)在花粉块之外包围一层胶粘物质。
The pollen wall of tetrads located in different positions of a mature pollinium of Cym- bidium goeringii was examined with the electron microscope.and the compositions of wall ma- terials were also tested with different histochemical methods.In all tetrads of a pollinium,the pollen wall can be distingished into an exine and an intine,but the exine may be varied grea- tly according to the tetrad position in a pollenium.The part of the pollen wall(the outer wall)of the external tetrads,lying close,to the tapetum,is composed of two layers,i.e.the exine,and the intine.Theexine consists of tectum,granulate ectexine and endexine,without foot layer.The intine is cellulose in nature.In the outer wall between different groups of tetrads and in the inner wall within an individual tetrad,the structure of ectexine becomes simple and the deposition of sporopollenin is roduced The degree of reduction of ectexine nic- reases from the outer to inner tetrads in several external layers of a pollinium,and even the internal tetrads have a reduced ectexine or lack of it. The present study also demonstrates that the mechanism of pollen aggregation into a pol- linium is built on a combined effect of the following features:(1)connected bridges formed by intine between two pollens within a tetrad,(2)formation of cytoplasmic channels between two pollens within a tetrad,(3)incomplete cell wall formation within a tetrad,(4)little size of tetrads and compact arrangement of mature tetrads and(5)a sticky viscin material surrounded on the outside of a pollinium.
关键词
春兰
花粉壁
结构
Pollen wall
Pollinium
Cymbidium goerii
