Relationship Of Rice Quality And Dynamics Of Enzyme Activities During The Denucleation Development Of Rice Endosperm Cell PCD

Using different varieties with varied quality as materials, dynamics of enzyme activity of SOD, CAT and key enzymes of starch synthesis in starchy endosperm cell and relation between them and denucleation development of endosperm cell during filling stage were studied; Structural variation and development of PCD process of endosperm cell during endosperm developing stage of an indica rice variety zhongxian 8836 were observed with transmission electron microscope (TEM); Endosperm cell structures, development of starch plastid and microstructures before and after gelatinization during grain filling process were observed with scanning electron microscope (SEM);Thermodynamic property of gelatinization and feature of texture quality of different varieties were studied with differential scanning calorimetry (DSC) and texture analyzer(TA),the amylose, amylopectin and intermediate fraction of rice with varied quality were isolated by chemical methods, whose relative contents were measured, the main results were as follows:1. Starchy endosperm nucleus begin to deform on the fifth day after blooming with the developing of endosperm cells, intermembranous space composed of intrinsic-extrinsic layer of nuclear envelope deform and enlarge in many positions, the chromatin condense and produce some flocculent masses of different sizes, which disperse in cellular internalization or stick to the internal surface of nuclear membrance. On the sixth to seventh day after blooming, the denucleation development accelerate, nuclear deformation and disintegration also aggravate. On the 10th day after blooming, it is impossible to see the nuclear relic in the cells denucleated earlier which have finished their denucleation. Through Evan's blue staining method, we found the occurrence of cellular denucleation is random in position. All cells in the tissue of starchy endosperm of the variety Zhongxian 8836 have finished their denucleation on the 12th to 13th day or so after blooming. At the same time of denucleation development of endosperm cell, a part of mitochondrions begin to disintegrate, the internal cristae collapse and disappear slowly, the interior of mitochondrion change into bubble and are full of starch grains.2. Nuclear disintegration in rice starchy endosperm cell during denucleation process has the common feature with the PCD of general plant and animal, denucleation is the first period of PCD in starchy endosperm cell, denucleation process of starchy endosperm cell present some special phenomena, for example, cell nucleus is the first cell organ dying out, nucleus is absorbed and digested by starchy plastid in the cell during developing stage, nuclear aggregates produced in the process of starchy endosperm cellnuclear disintegration are similar to the apoptosis body. Which belong to special PCD phenomena.3. Enzyme activities of SOD and CAT are higher in endosperm cell during denucleation developing stage, the difference of enzyme activity of CAT between different varieties is not notable. The bigger the chalkiness of the variety is, the faster the enzyme activity of SOD decreases, if the condition is reverse, the result is reverse. Enzyme activities of SOD and CAT in the varieties of higher chalkiness are slightly lower than those of lower chalkiness, whose grain age shorter, the ripening speed faster.4. The metabolic activity of rice starchy endosperm cellular denucleation developing stage is the highest in whole developing stage, no matter grain weight increase or filling rate are both the fastest, enzyme activity of starch synthetase is higher. Enzyme activity of AGPase in the varieties of higher chalkiness will reach peak value on the 9th day after blooming, while that of lower chalkiness will delay 3 days, the differences are not obvious comparing the dynamics of enzyme activity of AGPase between the varieties of different content of amylose; enzyme activity variance of SS in different varieties is great, enzyme activity of SS will keep increasing after blooming, enzyme activity of the va...