濒危植物马蹄参的大孢子发生和雌配子体发育

为探讨马蹄参(Diplopanax stachyanthus Hand.-Mazz.)濒危机制与雌性生殖发育的关系,采用石蜡切片法观察马蹄参大孢子形成和雌配子体的发育过程。结果表明,马蹄参雌蕊单心皮,子房下位,1室,1枚胚珠。胚珠横生于短片状胎座上,具单珠被,厚珠心。单孢原细胞自珠心1~2层表皮细胞处分化;大孢子四分体为直线形。成熟胚囊中,2个极核在受精前融合为次生核,3个反足细胞不发达,较早退化;二核胚囊时期出现二核分裂不均且较小核退化消失的异常发育现象。因此,马蹄参雌配子体发育过程中出现异常现象是造成其结实率低的主要原因。

Megasporogenesis and Development of Female Gametophyte of Endangered Plant Diplopanax stachyanthus

In order to understanding the relationship between the endangered mechanism and the female reproductive development of Diplopanax stachyanthus Hand.-Mazz., the megasporogenesis and development of female gametophytes were observed by using the paraffin section method. The results showed that the pistil of D. stachyanthus was single carpel, ovary inferior with one locule and one ovule. The amphitropous ovule located on a short flake placenta with single integument and thick nucellus. The single sporogonium differentiated from epidermis of nucellus; the megaspore tetrad was linear. In mature embryo sac, two polar nucleis fused into secondary nucleus before fertilization, three antipodal cells were undeveloped and degraded. The abnormal development happened at 2-nucleate embryo sac stage, two nuclei division was uneven and the small nuclei degenerated and disappeared. Therefore, it was suggested that the abnormal development of D. stachyanthus female gametophyte was the main reason for low setting rate.