白刺(NitrariasibiricaPall.)胚胎学的研究 1.小孢子和雄配子体的发育

The Studies on the Embryology of Nitraria subirica Pall.1.The Development of Microspore and Male-gametophyte

花药药壁发育为基本型.成熟绒毡层细胞具双核,属分泌型,小孢子母细胞减数分裂为同时型,小孢子四分体排列为四面体形,单核小孢子第一次有丝分裂时,纺锤体始终与小孢子细胞长轴平行.生殖核先于营养核形成,胞质分裂极不对称,营养细胞与生殖细胞间具明显的、非肼胝质性质的壁.散粉时花粉粒为2细胞,细胞内贮藏丰富淀粉粒.花药各部分组织中始终富合淀粉粒,在小孢子及雄配子体发育过程中,淀粉的消长显示一定的功能相关规律.小孢子母细胞在减数分裂前期时开始积累肼胝质壁;刚释放的小孢子肼胝质荧光弱,液泡期小孢子具较强的肼胝质荧光.

A series of events during the development of the megaspore and the female gametophyte of .Nitraria sibirica was studied by means of the regular histo-cytolgical,histochemical,and fluorescence microscopic methods.The main conclusions are as follows. The gynoecium is tricarpeUary,syncarpous comprising a triloculus ovary contains one ovule in each loculus,but only two ovule can develop and form one seed ultimately.The ovules are anatropous,bitegminal and crassinucellar.The micropyle is formed by the both inner and outer integument.The single hypodermal archesporial cell undergoes twice division forming the parietal cell and the secondary sporogenous cell,the latter functioning as the megaspore mother cell.The megaspore mother cell undergoes the usual meiotic divi- sion to form linear tetrads of megaspores.Generally,the chalazal megaspore functions while the remaining three degenerate.The functioning megaspore undergoes three successive mitotic division forming the eight- nucleate,Seven-celled embryo sac,and its development is the Polygonum type.The antipodal cells degener- ate before fertilization.With the beginning of the megaspore mother cell meiosis,the starch increases gradu- ally in ovule tissue.Till the stage of fertilization and embryo development,the starch grains is always rich in the cells of the nucelluce and the integuments.The callose fluorescence appears simultaneously at the both chalazal and micropylar poles at the stage of megaspore mother cell meiosis,and disappears first at the cha- lazal end of the functional megaspore.