| In 2006–2008 growing seasons, on the condition of pot culture and pond culture respectively, the studies were carried out to investigate the effects of post-anthesis water deficit and the irrigation at different developmental stages on the starch accumulation and granule size distribution in winter wheats with different amylose content. The principle results are as following:1 The granule size distribution characteristic of starch in wheat grainAt maturity, the diameter of starch granules in wheat grain changed in the range of 0.4–50μm. Wheat grain starch granules had a bimodal curve in the volume and surface area distribution, in which the valley particle diameter is the cut-off of A-granules and B-granules, 10μm. A unimodal curve with the granule diameter less than 1μm at the peak was seen in starch granule number distribution.The results of subdivided ranges of volume distribution showed that a higher volume percentage of diameter <10μm granules, particular <5μm granules, was typical of Nuomai50206 in comparison with other cultivars, and opposite results ware seen in Jinan17 and Shannong15.The analysis of correlation showed that amylose content was negatively correlated with the volume of <10μm and positively correlated to >15μm starch granules, respectively, suggesting that small starch granules (<10μm) are low in amylose contents, whereas, big starch granules (>15μm) are high. Post-anthesis water deficit reduced the B-granules volume % and surface area % in Nuomai50206 and Gaocheng8901, increased the proportion in Weimai10, while the effect on those in Jinan17 and Shannong15 was not significant. When it comes to the number distribution, post-anthesis water deficit cut down the number% of granules <2μm, significantly in all cultivars.We could conclude that the grain starch granule size distributions of Jinan17 and Shannong15 with higher amylose content were less affected by water deficit, than those of Nuomai50206 and Gaocheng8901 with lower amylose content. The results here are valuable for obtaining high quality for different end-uses in wheat production.2 The dynamic changes of starch accumulation and granule size distribution of starch in wheat grains during grain fillingDuring grain filling, the content of starch in wheat grain increased gradually. Post-anthesis water deficit affected the starch accumulation significantly, and by turn, decreased the starch content in mature wheat grains. The experiments of irrigation at different developmental stages indicated that appropriate water content was helpful to obtain high starch content in wheat grains.During the grain filling, the volume distribution of starch granules in wheat grain showed a bimodal curve, and the valley particle diameter was always near the 10μm. At 7 DAA, two types of granules, A-granules and B-granules, were found in wheat grain starch. 7–14 DAA, A-granules formed greatly. After 21 DAA, the volume percentage of diameter <10μm granules increased gradually.The number distribution of starch granule in wheat grains gave a unimodal curve with the peak diameter 0.5–1.1μm at different stages after anthesis. During 28–35 DAA, the peak height of number distribution in Shannong15 increased significantly, indicating that the minimal type of granules formed largely.In the surface area distribution, a unimodal curve was found at 7 DAA, and bimodal curves at other stages. In the bimodal curves of surface area distribution, the second peak height was higher significantly than the first one. Combined with the volume distribution, a conclusion could be reached that the surface area of starch granule was determined by the small starch granule (B-granules), while the volume, by the large granule (A-granules).3 Sucrose metabolism in flag leaf and grain of wheatDuring grain filling, the total soluble sugar content in flag leaf of wheat rose first and fell afterwards. The content levels varied with the cultivars: the total soluble sugar content in flag leaf of Nuomai50206 was higher than those of other cultivars. At maturity, the total soluble sugar content in flag leaf of Nuomai50206 remained relatively higher, while the content in Shannong15 was lowest.Post-anthesis water deficit decreased the total soluble sugar content in flag leaf of wheat. In the irrigation treatments at different stages, T4 increased the total soluble sugar content at prophase of grain filling, and decreased it at anaphase. The changes of sucrose content in flag leaf were identical with those of total soluble sugar content.The sucrose content and the total soluble sugar content in grains decreased gradually during grain filling. The effect of post-anthesis water deficit and irrigation at different stages on the sucrose content was smaller than that on contents in flag leaf.
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