| The field experiment was carried out at the Experimental Station of Shandong Agricultural University from 2006 to 2007. Two wheat cultivars, Jinan17 (JN17, multi-spike type) and Shannong8355 (SN8355, large-spike type), were used for investigating the effects of source-sink regulation(CK,RS,RL) on starch accumulation , starch granule Distribution , yield and grain starch quality formation of winter wheat.The principal results are follows:1. The granule size distribution characteristic of wheat starch1.1 The starch granule size distribution of wheat cultivars differing in quality typeAt maturity, wheat contained two types of starch granules: smaller B-type granules(<9.8μm) and large A-type granules(>9.8μm). The diameter of starch granules changed in the range of 0.37～52.6μm. Volume distribution of starch granules showed the typical two populations with peak values in 5μm and 25μm, respectively. The number distribution of starch granules exhibited a single peak curve with peak at 1μm. The number of B-type starch granule comprised over 99% of the total starch granule numbers, indicating that the number of starch granules was mainly small starch granules. Similar to the volume distribution, the surface area distribution also showed double peak curves with peak at 2.8μm and 23μm. The B-type starch granules comprised about 80%, and A-type starch granules contributed about 20% of the total surface area.The diameter of starch granules of both cultivars changed in the range of 0.37~52.63μm. The volume and surface area percentage of A type starch granule of mature grain in Shannong 8355 were obviously higher than those of the grain in mid-filling stage, the increasing rates were respectively 17.65~22.88%,35.8~39.05% under irrigation conditions, and 1.46~2.82%,7.05~8.12% under rainfed conditions. As to B type starch granule, the results were contrary to A type starch granule, the decreasing rates were respectively 34.78~40.47%,11.73~13.77% under irrigation conditions, and 5.08~7.67%,2.52~3.43% under rainfed conditions. Concerning volume and surface area percentage of A,B starch granule of Jinan17, the dynamic changes in both mature and mid-filling grains were similar to Shannong8355, the increasing rates of A type starch granule were respectively 1.56~5.98%,2.96~9.92% under irrigation conditions, and 1.76~4.52%,1.28~8.63% under rainfed conditions. The decreasing rates of B type starch granule were respectively 3.46~12.27%,1.02~4.18% under irrigation conditions, and 5.31~9.87%,0.58~3.13% under rainfed conditions. In conclusion, the volume and surface area percentage of A type starch granules were significantly enhanced by leaf-removal and decreased by spike-removal, the results of B type starch granules were contrary to those of A type starch granules.1.2 The dynamic changes of starch granules in wheat endospermThe number of starch granules in wheat endosperm exhibited single peak curves with peaks at 0.5～1.1μm. At 5 DAA, the starch granules showed a broad band of variously sized granules up to 20μm diameter. The diameter band of starch granules enlarged to 30μm at 10 DAA. By 15 DAA, a burst of synthesis created a new population of small starch granules, which reduced the number proportion of big starch granules. At 25 DAA, the number of starch granules less than 0.6μm increased and bigger starch granules in diameter reduced continuously, indicating that new granules were still synthesized, however, the magnitude of increase reduced. At 35 DAA, it is mainly the enlargement of small granule size class diameter, not the other granule size class diameter.2. Starch accumulation in wheat differing in spike typesThe simulation with Logistic equation showed that it was accumulation duration and SAR that determined the starch accumulation in large-spike type cultivars. under different irrigation conditions (irrigation and rainfed conditions) in this study. Jinan17 is compared with Shannong8355, Large-spike type cultivars had stronger ability of starch synthesis and sucrose supply than multi-spike type cultivars at mid-late grain filling stage.There was significant effect of source-sink regulation on starch accumulation of both the cultivars under different irrigation conditions. The total starch and amylopectin contents of spikelet-removing treatment were markedly decreased, but amylose content of spikelet-removing treatment was increased, compared with control. Then the ratio of amylose and amylopectin of spikelet-removing treatment was significantly higher than that of control.At irrigated and rainfed conditions, the starch content in weak large-spike type cultivars were significantly higher than that in multi-spike type cultivars during grain filling period, indicating that large-spike type wheat had stronger ability of starch synthesis than multi-spike type wheat. Compared with rainfed condition, the irrigation was more beneficial for the starch accumulation in both quality type cultivars. Rainfed condition was more beneficial for the improvement of starch synthesis ability at early filling stage, whereas irrigated condition was in favor of starch accumulation at late grain filling.3. The grain yield in wheat differing in spike typesThe irrigation had obviously regulation to the yield and its constitution factor to the two kinds of wheat. The irrigation could effectively enhance the ear of number and thousand grains, and obviously increase had happened to the ear of grain .Compared with the yield of big ear type SN8355, multi-spike type JN17, the yield of the later was higher .The yield of the wheat can be greatly increased by the irrigation, but excessive irrigation could make the yield of the multi-spike type reduced. Because of the coordinated ability of big ear type SN8355 was worse, in the production should suitably increase the basic seedling to display its potential.4. Effects of source-sink regulation at different grain filling stages on the starch formationThe sucrose in spikelet-removing treatment flag leaves of two cultivars had remarkable difference than CK, Results indicated that RL |
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