College of Life Science, China West Normal University, Nanchong, Sichuan Province 637009, China.
Biol Res. 2012;45(4):393-8. doi: 10.4067/S0716-97602012000400011.
The sporogenesis and development of gametophytes in Tetracentron sinense Oliv. were studied with light microscopy. The anther has four microsporangia; its primary anther wall consists of an epidermis, an endothecium, one or two middle layers and one glandular tapetum. Simultaneous cytokinesis follows meiosis, forming a tetrahedral tetrad. Mature pollen grains are two-celled at the time of anther dehiscence. Its ovule is anatropous, bitegmic and crassinucellate; the development of the female gametophyte is of the monosporic 8-nucleate Polygonum type. Significantly, some striking features were first found in T. sinense: (1) anther dehiscence occurs soon after the endothecium fibrously thickens and the intersporangial septum degenerates; (2) tapetum degeneration is retarded, persisting up to the stage of two-celled pollen grain; (3) a few cellular events such as the vacuolization and the contraction and deformation of the pollen mother cell (PMC) and microspore are not normal at the PMC, dyad and tetrad stages. The abnormalities during male reproduction might be one of important factors resulting in the poor natural regeneration of T. sinense.
采用光学显微镜研究了伯乐树（Tetracentron sinense Oliv.）的小孢子发生和配子体发育。花药具 4 个小孢子囊，其初生壁由表皮、内皮层、1-2 层中层细胞和 1 层腺质绒毡层组成。减数分裂后紧接着同时进行细胞质分裂，形成四面体型四分体。成熟花粉粒在花药开裂时为二细胞型。胚珠倒生，具双珠被和厚珠心；雌性配子体的发育为单孢子八核蓼型。伯乐树中首次发现了一些显著特征：（1）在中层细胞纤维状加厚和隔壁退化之后，花药很快开裂；（2）绒毡层退化延迟，一直持续到二细胞花粉粒阶段；（3）在小孢子母细胞（PMC）、二分体和四分体阶段，一些细胞事件，如 PMC、二分体和四分体的液泡化以及花粉母细胞（PMC）和小孢子的收缩和变形，并不正常。雄性生殖过程中的异常可能是伯乐树自然更新不良的重要因素之一。
