Gametophyte development in Asperugoprocumbens (Eritrichieae, Boraginaceae)

摘要

Reproductive organs and embryological characters consisting of microsporogenesis, macrosporogensis,andgametophyte developmental process were studied in Asperugoprocumbens. The results showed that anther is tetrasporangiate and consisting of four-layered wall with dicotyledonous type development. The middle layer and tapetumweredisappeared during development. Tapetumis combination of secretory and plasmoidal type. Tetrahedral tetrads with simultaneous cytokinesis were produced. Pollen grains were pear shaped, 2-celled and 6-colporate at the shedding stage. The ovule is unitegmic, anacampylotropous, tenuinucellate, funicular and embryo sac development is of Polygonum type. A single archesporial cellwasformed that act as megasporemother cell. The chalazal ormicropylarmegaspore of the linear or T-shaped tetrad functions as the functional megaspore and produced gametophyte. The mature embryo sac is consists of an egg apparatus at the micropylar end, a central cell in adjacencies of egg apparatus and five antipodal cells at the chalazal end.