The division process of endosperm in rice and its influencing factors were investigated. Total dissection, resin embedding and sectioning under light and transmission electron microscopes were used to observe the division patterns of free nuclei and cytological characters of an endosperm. The various division patterns of free nuclei in rice endosperm included mitosis, amitosis, and the mitosis to amitosis change without an interphase. The division velocity of free nuclei in rice endosperm varied with the internucleus distance. Comparing to a cluster, the division velocity increased when the free nuclei were separated from each other. Moderately higher temperatures also enhanced the proliferation and shortened the division cycle of free nuclei in rice endosperm. To a certain extent, nitrogenous fertilizer applied at the booting stage together with a moderate drought treatment accelerated the division of free nuclei as well.
LIU Man-xi WANG Zhong WU Xiao-mei CHEN Yi-fang GU Yun-jie
The germination of pollen grain in vitro and the growth of pollen tube in the pistil of rice were observed with a microscope. The stigma was removed at different time points after pollination to study its effect on seed setting rate. The rice pollen grain started to germinate at 2 min after pollination and the pollen tube penetrated stigma into style in 5-10 min, 30 min later the end of pollen tube reached the bottom of ovary, and only some pollen tubes arrived at embryo sac at 40 min after pollination. Meanwhile, a small amount of callose began to deposit in the pollen tubes, a great deal of callose was observed at 50 min after pollination, whereas the pollen grain began to shrink. The growing rates of pollen tube in the rice stigma, style and ovary were 1500, 5000, and 5400 μm/h, respectively. The seed setting rate was quite low when the stigma was removed at about 10-15 min after pollination, gradually increased when it removed at 20 min to 50 min after pollination, and over 60% when it removed at 50 min after pollination and finally tended to be stable.
CHEN Shi-qiang WANG Zhong LIU Man-xi XIE Zhao-wei WANG Hui-hui
