虎榛子小孢子发育与雄配子体形成研究

Studies on Microspores Development and Male Gametophytes Formation of Ostryopsis davidiana Decne

采用石蜡切片法研究了虎榛子小孢子发育与雄配子体的形成过程,以探讨桦木科植物的属间胚胎学关系.结果显示:(1)虎榛子从小孢子母细胞到雄配子体形成约经历6个月,其间以小孢子母细胞的形式越冬,次年4月中旬花药成熟,花粉粒散粉.虎榛子花药2室;花药壁为基本型,最外层是表皮1层,其内部分别是药室内壁1层、中层2～3层和绒毡层1层.绒毡层在花粉发育过程中原位消失,为腺质绒毡层.(2)小孢子母细胞减数分裂为同时型,四分体呈四面体形.(3)花粉粒通常具有3个萌发孔,少数具有4个萌发孔,孔处外壁不加厚.成熟花粉粒多数为二细胞型,极少数三细胞型.(4)虎榛子较白桦的雄蕊数增多,四分体形式趋向统一化.结果表明,广义桦木科的概念更合理,虎榛子属和桦木属的进化路线不同,同时桦木科植物越冬休眠形式可以作为它们属间分类的一个新依据.

Ostryopsis davidiana Decne. belongs to the family Betulaceae. In order to further probe the embryological relationships among genera of the family, the development process of its microspores and the formation of male gametophytes were studied in the paper with the normal paraffin sectioning. The results are as follows.O, davidiana approximately experience 6 months from pollen mother cell to mature pollen grain and survive in winter in the form of pollen mother cell. Pollination occurs in middle of April. Anthers are bisporangiate. Anther wall develops according to the basic type,and it consists of epidermis,endothecium,2-3 middle layers,and the tapetum. Tapetum grows according to the glandular type, and then disappears in its original position. Meiosis of pollen mother cells is simultaneous type. Tetrads are tetrahedral. Pollen grains are three-germinating pore and rarely four pores. The wall of germinating pore is not thickened. And most of mature pollen grains are 2-celled,and rarely 3-celled. Compared with Betula platyphylla Suk. ,O. davidiana has more stamen number and tetrad trends unitizing. These results indicated that the concept of generalized Betulaceae is more reasonable,Ostryopsis Decne. and Betula L. develop in the different ways and the form in which the family Betulaceae survives in winter can be a new evidence of difference among its genera.