Study On Some Physiological Activities Changes Of Rice Caryopsis

Four rice varietics, whose grain weight were remarkably differnt, were taken as plant material in this experiment. And the changes of fresh/dry weight, dehydrogenase activities, respiratory rate, ATP content, activities of CAT, SOD,POD, content of soluble protein and so forth within days after flowering of their caryopsis, the changes of ultrastructure, chlorophyll content, pholosynthetic oxygen-evolving activities, and Rubisco content of the pericarp of big grain japonica and small grain indica were highlighted, and the main results were as follows:(1) fresh and dry weight of caryopsis shows a increase in the form of "S", and its increase rale was coherent with its water content and its physiological activities, high water content and high physiological activity will lead to high increase in fresh anil dry weight; and a long time to maintain its physiological activities, and Ihe fresh and dry weightwill increase in a longer time.(2) many starch grain and chloroplast in the middle layer cell of the well developed ovary wall; chloroplast is composed of chlorophyll and the key enzyme of photosynthesis Rubisco. The pericarp has the ability of photosynthesis andoxygen evolving, and many starch used for the growth of pericarp cell was accumulated in ovary wall at early stage of development.(3) comparison between the varieties of big grain and small grain, Big grain caryopsis has stronger milking potential, slower water loss, and a longer period of maintaining milking; while small grain caryopsis has weak milking potential, fast water loss, and a shorter period of maintaining milking; Activities of dehydrogenese, respiralory activities of big grain caryopsis were greater than those of small grain caryopsis, and it has longer period of maintaining activities than the small graincaryopsis; Activities of SOD and CAT, which has sonic relationship with cell senescence, were higher than those of small grain varieties, but POD activities were smaller than thai of small grain varieties, and it has a longer period of maintaining the activities ol enzymes the lime for the big grain caryopsis to synthesize protein was longer than small grain varieties; Compared with big grain japoniea and small grain indica, large amount of starch were accumulated at ovary wall during early period of development, the ovary wall cell has a longer growth period, pericarp enlarge significantly 15 days after flowering, and small amount of starch accumulate in ovary wall of small grain indica, the cell has a small growth amount, the pericarp cell begin to contract after flowering; the chlorophyll content, the photosynthetic acitivities and content of chylorophyll of big grain japonica pericarp were all smaller than small grain indica; thus it can be concluded that reason for the big sizc of the big grain lies in that the sink has a higher activities and stronger ability of anti-senescence , thus a stronger milking potential and a longer period of milking activities were maintained; on the other hand, il has a bigger volume to accept assimilate,(4). compared between joponica and indiea, japonica has slower milking rate at early stage, but has a bigger milking rate than indica at late stage, and can maintain a longer milking period; japonica has a lower respiratory rate and ATP content at early stage, but has higher physiological activities at late stage than those of indica; Activities ol SOD and CAT during all the period of japonica were higher than those of indica; chlorophyll content, photosynthetic activities and Rubisco content of japonica pericarp were higher than those of indica; it could be concluded that the reason for the longer period of milking were because that it has a stronger ability of anti-senescence , thus the activity of caryopsis pericarp and endosperm cell were maintain, and the acceptance of milking material were ensured.