摘要
成熟胚囊被珠被绒毡县包围,由卵器、具次生核的中央细胞以及数目为1至6个反足细胞组成。传粉后6小时左右,雌、雄性核融合。配子融合同精核与次生核的融合几乎同时发生;精核与次生核融合速度快于配子融合。甜叶菊受精作用属于有丝分裂前类型。传粉后8小时左右,初生胚乳核分裂,其分裂方向可与胚囊长轴平行或垂直,从而形成最初的两个胚乳细胞。胚乳细胞前5次分裂是同步的。心形胚阶段,胚乳细胞呈现被消化吸收的迹象。胚乳发育属细胞型。传粉后10小时左右,合子第一次分裂,为横分裂。胚胎发育属紫菀型。
The mature embryo sac is surrounded by en lothelium tapetum.It is composed or an egg apparatus,one central cell with secondary nucleus,and 1—6 antipodal cells.About the 6th hour after pollination,female and male nuclei fuse with each other.The syngamy occurred almost simultaneously with the fusion of an other sperm nucleus and the secondary nucleus,but the velocity of the latter is faster than that of the syngamy.The fertilization of Stevia rebau- diana Bertani belongs to the premitotic type.About the 8th hour after pollination,primary en- dosperm nucleus is in mitosis,its dividing orientation may parallel or at right angle to the long axis of the embryo sac,and gives rise to two initial endosperm cells.The first five divisions of the endosperm cells are of synchronism.At the stage of heart-shaped embryo,the endosperm cells show the signs of digestion and absorbed.The endosperm development is of the cellular type.About the 10th hour after pollination,zygote divides for the first time.The division of the zygote is always transverse.The embryo development conforms to the Asterad type.
关键词
甜叶菊
受精作用
胚乳
胚
Stevia rebaudiana
Fertilization
Embryo and endosperm
