---

作 者 ：Li Kun-pei and Zhang Qi-tang

Keywords:Sweet potato, Embryology, Fruit, Seed,

Abstract:This paper deals with the development of the embryo and the formation of the fruit for lpomoea batatas Lam. based on the observation of its flower bud differentiation, megasporogenesis and the development of the female gametophyte, microsporogenesis and the development of the male gametophyte. The pollen grain germinated on the stigma about 10–30 min. after pollination. The pollen tube penetrated the transmitting tissue in the middle of the style between 30–60 min. after pollination. After 2 hours the tip of the pollen tube reached the micropyle. Double fertilization completed after 5 or 12 hours then the zygote and the endosperm nucleus formed. The first mitotic division of the endosperm nucleus takes place about 12 hours after pollination, earlier about 3 hours than the first division of the zygote, the latter gives rise to a terminal cell and a basal cell by a transverse division. The second division is transverse in the terminal cell, forming two cells. The basal cell divides longitudinally into two adjoining cells. The terminal cell becomes the proembryo with four cells, and at the same time, the basal cell becomes the suspensor with four cells after 41–52 hours. The proembryo gradually becomes globular, cordate and torpedo-shaped, respectively about 96–120, 144–156, 168-192 hours after pollination. The cotyledons of the embryo gradually prolongate 10 days after pollination. The embryo almost completes its development within 21–30 days after pollination. he fruit is a capsule. The ovary gradually swells 3–4 days after pollination, then forms fruit, which ripens about 21–30 days after pollination, 2R.=4–8 mm. A fruit contains 1–4 seeds. 7,000 fruits were analysed in 1983, the results are as follows: 64.6% of then with only one seed in a capsule, 31.8% two seeds, 5.48% three seeds and 0.1% four seeds. The seeds are small, 2R. from 3.84 mm to 2.84 mm. The shape and the weight of the seeds are different from each other because of difference in number of seeds within a capsule.

---