Starch Granule Size Distribution from Seven Wheat Cultivars Under Different Water Regimes

Seven wheat cultivars with different starch contents were used as materials to investigate the distribution of grain starch granule size under irrigated and rainfed conditions. In mature grains, the diameter of starch granules was 0.37-526 mu m, and the percent volume distribution showed a two-peak curve with the mean particle diameter of 5 (B-type) and 25 mu m (A-type) a each peak. The volume percnetages of A- and B-types were 52.7-65.5% and 34.5-47.3%, respectively. A two-peak curve is also shown in percent surface area distribution of starch granules, but only one peak in percent number. Both irrigated and rainfed conditions had a significant effect on the starch granule size distribution of the seven cultivars. As compared with irrigate treatment, rainfed treatment affected the distribution of starch granules in grains of all cultivars through increasing the volume percentage and surface area percentage of 2-9.8 and < 9.8 mu m starch granules and decreasing those of > 9.8 and > 18.8 mu m starch granules. The soil water deficit also decreased the contents of amylose and starch in grains and increased protein content, indicating that different water regimes had an evident effect on grain quality. According to correlation coefficients (r), the contents of amylose, starch, and protein in grains was significantly correlated with the volume percentage of starch granules with different diameter ranges.