水稻灌浆期籽粒中3个与淀粉合成有关的酶活性变化

在水培和盆栽条件下，研究了6个水稻品种(含籼/粳杂交组合、新株型品系)灌浆期强、弱势粒中ADPG焦磷酸酶(EC2.7.7.21)、淀粉合成酶(EC2.4.1.21)和淀粉分枝酶或Q-酶(EC2.4.1.18)的活性变化及其与灌浆充实的关系。3个酶的活性变化与籽粒灌浆动态相关联：淀粉酶最高活性出现的时间稍前或同步于最大灌浆速率的时间；ADPG焦磷酸酶

Changes in Activities of Three Enzymes Associated with Starch Synthesis in Rice Grains during Grain Filling

Six rice cultivars (including 2 japonica/indica hybrid combinations and 1 new plant type line ) were grown in water culture in green house/or in pots in screen house. The activity changes in three enzymes of ADPglusoce pyriphosphorylase (EC 2.7.7. 21), Starch synthase (EC 2.4.1.21) and starch branching enzyme or Q enzyme (EC 2.4.1.18) in both of superior and inferior grains and the relationship to grain filling were examined. The changes of three enzyme activities were associated with grain filling process. The time reaching a maximum of starch synthase activity was a little earlier than or synchronous with that of grain filling rate. Maximum ADPglucose pyrophosphorylase activity appeared at 3~6d before the highest grain weight. Q enzyme activity reached the maximum when grain weight was close to the highest. Each enzyme activity, in terms of the mean of whole filling period, the mean at early filling stage (3~12 days after flowering), and the maximum, were significantly or very significantly correlated with the mean filling rate, maximum filling rate, grain weight and fertilized grain filling percentage. Q enzyme had the largest coefficients in the three enzymes, on the whole. The enzyme activities in the grains of japonica/indica hybrid combinations were associated with their parents. Regulating source sink relationships or nutrient level in the plant by leaf cutting, spikelet thinning or nitrogen application at heading could increase or reduce the enzyme activities in grains, especially in the inferior at early filling stage. The results indicated that the three enzymes, especially Q enzyme, play an important role in rice grain filling. It is possible to breed a variety or a hybrid with good grain filling by using the parents with high activities of the enzymes in grains, and to increase grain filling percentage and grain weight by increase of the enzyme activities in grains at early filling stage.