| Abstract: | The present study was carried out to characterize the effects of soil water status, cultivar and grain position on starch granule size distribution. The starch granule size distribution and protein and starch content were determined from three wheat cultivars with reference to the position of the grain on the spike. The results showed that the contents of A‐, B‐ and C‐type starch granules were affected by soil water, genotype and soil water×genotype interaction. Grain position was significant for A‐ and C‐type starch granules. Genotype×grain position and soil water×genotype×grain position interactions only affected C‐type starch granules. Both basal and distal grains on middle spikelets contained three types of starch granules: smaller C‐type granules with diameters <2.0 μm, medium B‐type granules with diameters 2.0–9.8 μm and large A‐type granules with diameters >9.8 μm at maturity. Both percent volume and percent surface area distribution of starch granules in basal grains showed the typical three populations, and those in distal grains exhibited a two‐peak curve. The volume and surface area percentage of C‐type granules and protein content in basal grains were higher than that in distal grains, but those of A, B‐type granules in basal grains were lower than that in distal grains. Compared with irrigation, the percent volume and surface area of B, C‐type starch granules and protein content in basal and distal grains were significantly increased, and those of A‐type were evidently decreased in rainfed condition. |
