濒危植物裂叶沙参的大小孢子发生及雌雄配子体发育

SPOROGENESIS AND GAMETOGENESIS OF ENDANGERED ADENOPHORA LOBOPHYLLA HONG (CAMP ANULACEAE)

本文以近缘广布种泡沙参为对照,对濒危物种裂叶沙参进行了大小孢子发生和雌雄配子体发育的研究。裂叶沙参的药壁发育为双子叶型,绒毡层为腺质型,细胞含两核。小孢子母细胞在减数分裂过程中胞质分裂为同时型。小孢子四分体为四面体型,成熟花粉粒为2-细胞型。胚珠倒生,单珠被,薄珠 心,大孢子四分体为线形排列,胚囊发育为蓼型。成熟胚囊中两极核在受精之前融合为一个大的次生核。当胚囊发育至单核胚囊时,珠被的最内层细胞发育为珠被绒毡层。濒危植物裂叶沙参在大、小孢子发生及雌、雄配子体的发育过程中,未见有败育及其它异常现象;与对照种泡沙参相比,也未见有差异,这说明裂叶沙参的致濒原因不在于有性生殖过程。

Reported in this paper are the microsporogenesis, megasporogenesis and the development of male and female gametophytes of the endangered species Adenophora lobophyl-la. The anther is four-sporangiate with its wall composed of four layers: epidermis, fibrous endothelium, middle layer and glandular tapetum of binucleate cells. The cytokinesis of mi-crospore mother cell in meiosis is simultaneous, and tetrads are tetrahedral. Pollen grains are 2-celled at the dispersal stage. Ovule is anatropous, unitegmic and tenuinucellate with a hy-podermal archesporial cell developing directly as the megaspore mother cell which undergoes meiotic division and then forms a linear tetrad. The embryo sac is of Polygonum type. The polar nuclei fuse before fertilization. An endothelium differentiates when the uninucleate embryo sac forms. Comparative studies were made with the closely related and widely distributed species A. potaninii. No differences between them were found. No obstacle to sexual reproduction in this endangered species was observed. As a conclusion, no endangering factors were found to influence the sporogenesis and gametogenesis of A. lobophylla. According to our observision and the references on embryological studies of the Campanulaceae(s. 1. ), there is no evident differentiation in sporogenesis and gametogenesis in this family.