野菊Dendranthema indicum(L.)Des Moul的大孢子发生和胚囊的发育

MEGASPOROGENESIS AND THE DEVELOPMENTOF THE FEMALE GAMETOPHYTE IN DENDRANTHEMA INDICUM (L.) DES MOUL.

对菊科的野菊D.indicum进行了大孢子发生和胚囊发育的研究。单层的肥厚珠被起源于大孢子母细胞的基部附近。珠被内表皮早期就开始分化为珠被绒毡层。珠心属于瘦心式,单层的珠心表皮细胞在有效大孢子增大时开始解体。一个孢原细胞位于珠心表皮之下,直接起着大孢子母细胞的作用,大孢子四分体呈线形排列。胚囊的发育过程遵循正常的蓼型,但反足细胞核的产生有变化。胚胎学的资料不支持广义菊属Chrysanthemum L.的成立。著者在观察中发现因虫害形成胚囊吸器的例外情况。胚囊吸器的形成可能是因为胚珠不能满足胚囊发育所需营养而产生的一种生理适应。著者建议在今后的胚胎学研究中注意对珠被绒毡层进行观察和分类。

The present investigation deals with an embryological account of a taxon Dendranthema indicum, a member of the family Compositae.A single integument originates near the base of the megaspore mother cell, its inner epidermis begins to the differentiate into endothelium in the early stage. The ovule belongs to the tenuinucellate. The archesporium is one-celled, just beneath the nucellar epidermis cells, and directly functions as the megaspore mother cell. The nucellar epidermis cells begin collapsing in the early stage.A tetrad of megasporium is formed, which is linear shaped. The chalazel megaspore is functional. The development of the embryo sac conforms to the normal Polygonum type. The establishment of a wide sense of the genus Chrysanthemum L. is not supported by embryological informations. The author observes an exception to the rule in which the embryo sac extends through the cavity of the ovary and forms the embryo sac haustorium. The reason of the formation of the embryo sac haustorium is most probably that the ovule fails to provide necessary nutritions for the development of the embryo sac, the haustorium occurs as a physiogical adaption.The author thinks it aduisable to take notice of the classification of the endothelium and to accumulate informations for discussing the interrelationship between the patterns of the endothelium and the plant taxa.