美洲黑杨无性系Ⅰ-63花粉粒的发育和超微结构

<正> 美洲黑杨Ⅰ-63〔Populus deltoides Bartr.var.deltoides cv.“Harvard”(Ⅰ-63/51)〕自引种以来,生长良好,已经作为一种基因资源应用于新无性系的培育工作。Nagaraj在1952年曾对PopuluS deltoides的小孢子发生和花粉形态进行过研究,但选育为无性系并引种至我国的同纬度地区后,其小孢子的发育过程是否发生变化,选育应用时应注意哪些问题,却研究甚少。近年来,学者们对花粉超微结构做了大量工作,可惜至今还局限于少数植物,特别是草本植物。这里,我们试对美洲黑杨Ⅰ-63的小孢子发生、花粉发育和结构用光学显微镜进行了观察研究,并在此基础上观察了二细胞花粉粒的超微结构,希冀为这方面提供一些有益的资料。

ULTRASTRUCTURE AND DEVELOPMENT OF POLLEN GRAIN IN POPULUS DELTOIDES BARTR. VAR. DELTOIDES CV. HARVARD (I-63/51)

1 . Stamens are at their late stage of sporogenous tissue during the winter. Microsporogenesis follows the angiosperm pattern as usual. Anthers are tetradymous. The fully developed cell wall of the anther consists of four layers. When maturing, the cell of epidermis incteases in size and forms fibrous thickenings. The medial layer and endothecium are permanent. The cell of tapetum is usually binucleated. The glandular tapetum begins disintegrating at the tetrad stage. The formation of microspote follows the synchronous type. The tetrads are mostly the tetrahedron. Pollen grains are two-celled when shedding.2 . Under the scanning electron microscope, pollen grains of two-cells are mostly round. The surface of exine of the pollen grain is clouds-like, having small pores.3 . The ultrastructure of pollen grains involves the following main features. The wall of the pollen grain has an inline and a two-layer exine (inner and outer exine). The generative cell at this stage is surrounded by a wall of callose. Most part of the generative cell is occupied by the conspicuous and elliptical nucleus. The distribution of organelles is not even in the cytoplasm. Vegetative cells with larger volume are full of cytoplasm and all kinds of organelles. These organelles include plastids, dictyosomes, mitochondria, rough endoplasmic reticuium and various forms of vacuole, etc..4 . Chloroplast occurs in the medial layer cell of the wall of pollen sacs.5 . Questions concerning the ultrastructure and development of the pollen grain are discussed in this paper.