The Relationship between Sucrose Metabolism and Starch Accumulation during Grain Filling in Winter Wheat

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.