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The purpose of this study was to reveal the differences in development and size distribution of starch granules in endosperm of wheat grain in different spike positions.Two high-yield winter wheat (Triticum aestivum L.) cultivars,Jimai20 and Shannong1391,were chosen in this study.The results showed that grain number and weight per spikelet in different spatial position showed parabolic changes.Upper spikelets had the highest starch and amylose content followed by basal spikelets,whereas middle spikelets had the lowest.Starch and amylose accumulation showed the reverse form with their contents.The volume percents of B-type granule and A-type granule in grain of middle spikelets were remarkably higher and lower than those of basal and upper spikelets,respectively.However,no significant diffcrcnce occurred in the number percents of A- and B-type granule in grains among different spikelet position.Effect of spikelet position on the number distribution of small starch granule (＜2.8 μm e.d.) was significantly different.Number percents of starch granule 0.6-2.8 μm e.d.in grain of middle spikelets were remarkably higher than those of basal and upper spikelets,which showed that it is more conducive to the development of small starch granule in the middle spikelets.The results showed a significant positive relationship with the volume proportion of granules 22.8-42.8 μm e.d.but was negatively related to the volume proportion of granules ＜9.9 μm e.d.