Development Of Rice Caryopsis And The Dynamic Changes Of Its Physiological Activities During Its Development

Two varieties of Indica and two varieties of Japonica with significantly different grain weight were used in this experiment to study development of rice caryopsis and the dynamic changes of its physiological activities during its development, especially the relation between grain filling dynamic and its physiological activity, discuss the reason why big grain could form and why big grain varieties were easy to form chalkiness, the mechanism why different nitrogen treatment had different effect on grain filling dynamic and its physiological activity and its control methods, and provide scientific theory. Here are the main results:1. There's no stoma on the upper epidermis and there are bounds of plastids in the middle layer cells, under normal condition, the plastids locating in the outer side of middle layer cells are amyloplasts, while most of them in the inner side are chloroplasts that take on the olive- shape and have the developed lamellae structure; The absorption spectrum of pigment in pericarp is similar to that of chlorophyll in leaf; that is, there is one absorption peak in blue (440nm) and red (660nm) regions of spectra; The chlorophyll contents in pericarp, 5d, 10d and 15d after flowering, are 2.12μg /per caryopsis, 2.48μg /per caryopsis and 1.42μg /per caryopsis respectively; There exists the carbon-assimilating key enzyme (Rubisco) in the rice pericarp and its content reaches the highest on the 10th day after flowering; Although the pericarp had the photosynthetic oxygen-releasing function during the greening stage, its net photosynthetic rate was lower than that of respiration and had a longer lag time. Because of no stoma on the epidermis of pericarp, it was concluded that the CO₂ needed in photosynthesis come from the respiration of caryopsis; Moreover, the development and extension of pericarp have influence on the endosperm development and rice grain photomorphogenesis.2. At the primary stage, caryopsis water content was high, and decreased gradually during the rice grain filling. Fresh weight and dry weight of caryopsis increased quickly at the primary stage and then the increase trend was slowed down gradually; The grain filling rate in Indica was quicker than in Japonica at the primary stage, but stop filling earlier than in Japonica, too. The grain filling rate with big grain weight was quicker than that with small grain weight during all the filling stage in rice and stop filling later; Caryopsis water content and respiratory rate decreased after anthesis, and stop filling when water content decreased to 20% and respiratory rate decreased to 0.05μmol O2·mg FW-1·h-1; there is a positive relation between respiratory rate and ATP content, they both have a positive relation between water content; Dehydrogenase activity, CAT activity and SOD activity decreased as water content decreasing at the later stage of filling; There is a close relation between grain filling dynamic and its physiological activity. The longer the caryopsis keeps respiratory rate, Dehydrogenase activity, CAT activity and SOD activity, the longer the caryopsis keeps filling; The filling time of rice with big grain weight was longer than rice with big grain weight in Japonica.3. Nitrogen fertilizer utilization could preserve higher water content of rice caryopsis in later phase of milking, prolong milking time of rice caryopsis and maintained higher respiratory activity of rice caryopsis in later phase of milking in a longer time; and the time that some tissues in rice caryopsis maintain higher...