灌浆结实期弱光对水稻籽粒淀粉积累及相关酶活性的影响

 选用IR72（籼稻）和日本晴（粳稻）为材料，在开花后进行遮光处理，对弱光条件下籽粒淀粉和直链淀粉含量的动态变化及相关酶的活性进行了研究。在弱光条件下，两品种籽粒的淀粉含量减少，直链淀粉含量下降，蔗糖含量降低，ADPG焦磷酸化酶活性的变化较小，可溶性淀粉合成酶和颗粒结合型淀粉合成酶活性减弱，可溶性淀粉分支酶Q酶和颗粒结合型淀粉分支酶活性增强，淀粉去分支酶活性因品种而异，IR72表现为减弱，日本晴则为增强。相关分析表明，遮光下蔗糖输入量的减少量和淀粉合成量的下降量呈显著正相关；ADPG焦磷酸化酶和淀粉分支酶活性与淀粉积累速率呈显著正相关。分析指出，遮光下淀粉合成酶活性的降低与淀粉合成量的下降有关，淀粉分支酶活性的升高是直链淀粉占淀粉总量的比率减少的重要原因。

Effects of Weak Light on Rice Starch Accumulation and Starch Synthesis Enzyme Activities at Grain Filling Stage

Dynamic changes of starch content, amylose content, sucrose content and the activities of starch synthesis enzymes under shading treatment after flowering were studied using IR72 (indica) and Nipponbare (japonica) as material. Under shading treatments, starch, amylose and sucrose contents in the rice grain decreased, while ADP-glucose pyrophosphorylase (ADPGPPase) activity only changed a little, soluble starch synthase activity and granule bound starch synthase activity were decreased, soluble starch branching enzyme activity and granule bound starch branching enzyme activity were increased. Starch debranching enzyme activity was decreased in IR72, while increased in Nipponbare compared with the normal treatment. Correlation analysis showed that changes of starch content were positively and significantly correlated with changes of sucrose content under weak light. Both ADPGPPase activity and soluble starch branching enzyme activity were positively and significantly correlated with starch accumulation rate. It was implied that the decline of starch synthesis enzyme activities was relative to the decrease of starch component, and the increase of the activity of starch branching enzyme played an important role in the decrease of ratio of amylose to the total starch under weak light.