Two wheat culivars, SN12 (more grains per spike) and YZ4110 (less grains per spike), were used to investigate the activities changes of sucrose phosphate synthase (SPS) in wheat flag leaves and sucrose synthase (SS) in grains. The relationships of these enzymes to starch accumulation rate were also analyzed. The resuls showed that the activities of SPS in flag leaves maintained a high level within 14 d after anthesis, while that of SS in grains showed a single-peak curve. The peak activities and average activities of SPS and SS of SN12, which had more starch, were significantly higher than YZ4110. But there was no difference in the durations maintaining high enzymatic activities between the culivars. Simulating the process of starch accumulating with Logistic Equation showed that it was average accumulation rate, peak accumulation rate and initiating time,but not accumulation duration that determined the starch content. The relationship between the SPS activities in late grain filling and the starch accumulation rate was well fitted by Exponential Equations. And the relationship between the activities of SS in grains and the rate of starch accumulation was also well fitted by Exponential Equations. But the SPS activities in early grain filling didn't seem to play an important role in starch accumulation. An increasing exponential relationship existed between the rate of starch accumulation in grains and the SPS activity in late grain filling as well as the SS activity.%试验选用了山农12和偃展4110两个小麦品种,研究了小麦灌浆期旗叶磷酸蔗糖合酶(SPS)活性、籽粒蔗糖合酶(SS)活性变化与籽粒淀粉积累.结果表明,旗叶SPS活性在花后14 d内保持较高的水平,籽粒SS活性在灌浆期呈单峰曲线.山农12 SPS、SS的最大与平均酶活性均显著高于偃展4110,而两个酶较高活性持续期品种间无显著差异.用Logistic方程拟合淀粉积累过程表明,淀粉积累量的多寡主要受其平均积累速率、最大积累速率及积累启动时间早晚的影响.而与灌浆前期旗叶SPS活性变化关系不大,即灌浆后期的旗叶SPS活性对淀粉最终积累量的调节作用大于灌浆前期.籽粒淀粉积累速率与灌浆后期旗叶SPS活性和灌浆期籽粒SS活性呈增长型指数关系.
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