山茱萸配子体发育的研究

STUDIES ON THE DEVELOPMENT OF GAMETOPHYTES IN CORNUS OFFICINALIS (CORNACEAE)

山茱萸(Cornus officinalis)的花芽于4月底开始分化,11月初,雌、雄配子体发育成熟,次年3月开花。小孢子囊壁由表皮、药室内壁、2—3层中层细胞和绒毡层等5—6层细胞构成。发育成熟的绒毡层细胞具双核,属变形绒毡层。花药发育中形成外绒毡层膜。小孢子母细胞减数分裂过程中的胞质分裂为同时型。四分体呈四面体形。成熟花粉粒为2-细胞型,具3孔沟。胚珠具单珠被、薄珠心,在发育中形成承珠盘和珠被起源的珠孔塞。单个孢原细胞分化于珠心顶端表皮之下,直接成为大孢子母细胞。大孢子四分体为直列型,合点端大孢子具功能。胚囊发育为寥型。胚囊成熟后不久,两极核融合为次生核,3个反足细胞退化,在开花前2个月时,雌配子体成为四核4细胞的胚囊。有些发育成熟的助细胞的核位于细胞的合点端,珠孔端为大液泡所占据。次生核通常位于胚囊的合点端。

The floral bud of Cornus officinalis Sieb. et Zucc. began to differentiate at the end of April. In the beginning of November, female and male gametophytes reached their matura- tion. The flowers fell off in the following March. The wall of the microsporangium comprised epidermis, endothecium, two or three middle layers and a single layer of amoeboid tapetum with two nuclei. The extra-tapetal membrane was formed during the later stage of the develop- ment of anther. Meiosis of microspore mother-cell was normal and cytokinesis was of the si- multaneous type. The tetrad was tetrahedral in shape. The mature pollen grains were 2-celled and 3-colporate. The ovule was unitegminous and tenuinucellate. During the development of the ovule, some special structures were formed, e. g. hypostase and obturator which originated from the integument. A single archesporium differentiated immediately below the nucellar epi- dermis. It functioned directly as the megaspore mother-cell. This cell under went meiosis to form a linear tetrad. The chalazal megaspore was functional. The development of the em- bryo sac was conformed as the polygonum type. Two polar nuclei fused into the secondary nucleus and three antipodal cells degenerated soon after the embryo sac reached its maturation, at that time the female gametophyte had become an embryo sac which consisted of only four cells each with a nucleus just before two months of blooming. The nuclei of some synergids located in the chalazal part of the cells. Contrarily, the micropylar past of the synergids were occupied by a large vacuole. The secondary nucleus was usually located in the chalazal part of the embryo sac.