Study On Programmed Cell Death Of Endosperm In Rice

Using rice as materials,study on the changes of fresh/dry weight, water content, respiratory rate, activities of SOD, dehydrogenase and CAT along with the days after flowering of caryopsis. The structure change during endosperm development in rice (Oryza sativa L.) was studied by resin embedding combined with semi-thin section technology. The main results are shown as follows:(1) Fresh and dry weight of caryopsis shows a increase in the form of "S" along with the days after flowering. The increase rate of fresh weight is faster than the increase rate of dry weight. The water content reduces to 25% when the rice matures.(2) The respiratory rate decreased along with the development of caryopsis and the decrease of water content. The respiratory rate maintains a low level after twenty-fourth day flowering of caryopsis.(3) Back vascular bundle of caryopsis, embryo and endosperm have dehydrogenase activities at the early stage of caryopsis development. Only embryo has dehydrogenase activities at the late stage of caryopsis development.(4) The dead endosperm cell can be detected after ninth day after flowering by evan's blue staining. The cell death was discovered in the central part of starchy endosperm in rice and then expanded outward.(5) The amyloplasts in dorsal and center part of endosperm were developed better than those in abdomen. Starchy endosperm nucleus begin to deform on the fifth day after flowering with the developing of endosperm cells. The deformation of nucleus aggravated during the caryopsis development. When the nucleus disappeared, cell of endosperm were still alive. In some other amylum plant, we also find the phenomenon of nucleus deformation.(6) The cell death of endosperm in rice is controlled by genes. It belongs to especial programmed cell death(PCD).