Study On Relationship Between Rice Quality And Activities Of Key Enzymes Involved In Carbohydrate Metabolism During Grain Filling

5 japonica (Oriza sativa L.) vareties were investigated to reveal the relationship between eating and cooking quality and changes of the enzyme activities involved in carbohydrate metabolism during grain filling under different nitrogen nutrition. The results were as followed.Protein content in Shuiludaol and amylose content in Dongnong 416 were highest in varieties tested. Protein content and amylose content in Tengxi 180 were lowest. Tengxi 180 and Fushiguang had high taste value, max viscosity and break down than Shuiludaol and Dongnong 416, whereas had lower initial pasting temperature, final viscosity and setback. With increasing of nitrogen nutrition taste value, max viscosity, break down and consistence is decreased, whereas Protein content, initial pasting temperature, setback increased.Amylose content, amylopection content and total starch content were increasing during filling stage. Starch accumulation in the early stage is larger than in the late stage. Shuiludao 1 and Dongnong 416 had larger starch accumulation rate than Fushiguang and Tengxi 180. The tendency was reversed in the late stage.The dynamic changes of ADPglocose pyrophosphorylase(AGPP), soluble starch synthase(SSS), starch branch enzyme(SBE) were similar during filling stage. The enzyme activities were low in the early stage of grain filling and reach a peak in 18~24d after heading and decreased in the late stage of grain filling.The activities of enzymes in different filling stage and the time to reach a maximum were different with different quality types. Shuiludao 1 and Dongnong 416 were earlier to reach the maximum than Fushiguang and Tengxi 180 and enzyme activities decreased dramatically in the late stage of grain filling. The dynamic changes of Fushiguang and Tengxi 180 were stable during the grain filling and kept high activities in the late stage than other varieties. The study on the relationship between nitrogen nutrition and enzyme activities showed that nitrogen nutrition affected slightly on enzyme activities in the early stage. But the effect on SBE isABSTRACTsignificant at 24th, 30th day after heading. The activity of SBE was decreased with increasing of nitrogen nutrition, and AGPP, SSS had less change.The activities of AGPP, SSS and SBE were positively correlated with amylose content and negatively with amylopectin content and total starch content in early filling stage. It is reverse in the late stage. The activities were positively correlated with taste value in the early filling stage and negatively in the late stage. The effect of SBE on taste value was largest in 24th after filling (r=0.951**) the effect is smallest and couldn't reach a significant level.The activities of enzymes were negatively correlated with break down and high viscosity in the early grain filling. It is opposite at the late stage. The effect of SBE to amylography was larger than AGPP, SSS. The activity of SBE in 24th after filling was positively correlated with high viscosity, break down (r=0.810**,0.954**), and negatively correlated with consistent, setback (r=-0.949, -0.830**), whereas the correlation between SSS activity can't reach a significant level. The activity of SBE in 30th was positively correlated with break down (r=0.735*). the correlation between activities of AGPP and break down, consistence were 0.780* - 0.709 * .