车桑子大孢子发生与雌配子体发育

采用常规石蜡切片法,对车桑子大孢子的发生和雌配子体的发育进行观察,探讨车桑子自然结籽率低的原因和明确其胚胎发育特征。结果表明:(1)车桑子花柱有花柱道,子房3室,中轴胎座,横生胚珠,每心室两枚胚珠,双珠被,厚珠心,无承珠盘。(2)位于珠心表皮细胞下的孢原细胞经平周分裂产生造孢细胞,造孢细胞发育为大孢子母细胞,大孢子母细胞经减数分裂形成线性四分体,靠近珠孔端3个大孢子退化消失,靠合点端大孢子发育为功能大孢子,大孢子发生类型为单孢子发生型。(3)单核胚囊经3次有丝分裂形成7细胞8核的成熟胚囊,胚囊发育类型为蓼型。(4)花器官形态的变化和大孢子发育过程有一定联系,可根据雌花形态特征大致判断大孢子发育时期。研究认为,车桑子雌配子体发育过程中出现的胚囊不中空、游离核不进一步细胞化等异常现象,可能是导致车桑子自然结籽率低的原因之一。

Megaspores and Development of Female Gametophyte in Dodonaea viscosa

In order to know the reason of low natural seed setting rate and the characteristics of embryonic development of Dodonaea viscosa, the megasporogenesis and the development of female gametophyte were observed by using the method of paraffin section. The results were as follows:(1)D.viscosa had style canal and placentation is axial; the he ovary had 3 locules with two ovules per locule; the ovule was amphitropous, bitegmic, crassinucellate and without hypostase. (2)The sporogenous cells located under the epidermis of the nucellus produced sporogenous cells through the pericentric division. The sporoblasts developed into megaspore mother cells, and the megaspore mother cells formed a linear tetrad after meiosis, and 3 megaspore degeneration disappeared near the microspore end. The megaspore developed into functional megaspore and the type of megasporogenesis was monosporogenesis. (3)The mature embryo sac of 7 cells and 8 nuclei was formed by 3 mitosis of uninucleate embryo sac, and the development type of embryo sac was polygonum type. (4)The morphological changes of flower organs were related to the development of megaspore, and the development period of megaspore could be roughly judged according to the morphological characteristics of female flower. The results suggesting that a few abnormal phenomena such as the embryo sac was not empty and the no cellularization of the free nucleus in the development of female gametophyte may be one of the reasons leading to the low natural seed setting rate of D.viscosa.