白刺(NitrariasibiricaPall.)胚胎学的研究 2.大孢子和雌配子体的发育

用石蜡切片方法,结合组织化学及显微荧光技术研究了白刺大孢子及雌配子体的发育事态.主要结果为:雌蕊3心皮合生成3室子房.每室含1胚珠,仅2胚珠发育,最后形成1枚种子.胚珠倒生,双珠被,厚珠心,珠孔由内外珠被共同形成。孢原发生于珠心表皮下,一般1个,经两次有丝分裂形成壁细胞和次生造孢细胞,后者担任大孢子母细胞功能,母细胞经两次有丝分裂形成线形四分大孢子.珠孔端3个退化,合点端为功能大孢子.胚囊发育为蓼型,成熟胚囊由8核7细胞构成,受精前反足细胞退化。随母细胞减数分裂,母体组织中淀粉逐渐增多,到受精及胚发育时期,珠被和珠心中始终富含淀粉.在母细胞减数分裂时,肼胝质荧光同时出现在珠孔端和合点端,四分体时首先在功能大孢子端消失。

The Studies on the Embryology of Nitraria subirica Pall.2.The Development of the Megaspore and the Female Gametophyte

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.