三种禾谷类作物强、弱势粒淀粉粒形态与粒度分布的比较

本研究以水稻品种武运粳24和扬两优6号、小麦品种扬麦16和宁麦13及玉米品种登海11和农乐988为试验材料，分别提取其成熟期强、弱势粒的淀粉粒，观察比较不同作物及其强、弱势粒间淀粉粒形态和淀粉粒数量、体积和表面积分布特性。结果表明，3种禾谷类作物间淀粉粒形态大小差异明显，粒径表现为玉米>小麦>水稻。水稻淀粉粒呈有棱角的无规则状，小麦淀粉粒呈透镜体状或球体状，玉米淀粉粒呈椭球体状、多面体状或圆球体状。水稻和玉米淀粉粒数量、体积和表面积分别成单峰、三峰和双峰分布；小麦淀粉粒数量呈单峰分布，体积呈微弱的四峰分布，表面积呈三峰分布。水稻、小麦和玉米淀粉粒按各自粒径不同人为划分为小淀粉粒、中淀粉粒和大淀粉粒，分界线分别为1.5 μm和20.0 μm、5.0 μm和50.0 μm、4.0 μm和50.0 μm。3种作物籽粒淀粉粒的总体积主要决定于中淀粉粒体积。3种作物的强、弱势粒间小淀粉粒粒度分布比例及中淀粉粒所占数量比例没有明显差异，但各作物强势粒的中淀粉粒所占的体积和表面积比例均显著高于弱势粒，大淀粉粒的分布比例低于弱势粒。强、弱势粒的中淀粉粒所占体积比例与其淀粉积累量和粒重的高低变化趋势一致。表明淀粉粒体积是决定粒重的一个重要因素，增加弱势粒的中淀粉粒体积或减小大淀粉粒体积可望增加其粒重。

Comparison of Starch Granule Morphology and Size Distribution in Superior and Inferior Grains of Three Cereal Crops

Using two rice cultivars, two wheat cultivars, and two maize cultivars, we extracted starch granules to observe the morphological characteristics and to compare the differences in the starch granule number, volume and surface area distributions among the three crops and between superior and inferior grains of each cultivar. The results showed that significant differences were observed in starch granule morphology and size among the three crops. The diameter of starch granule showed an order of maize > wheat > rice. Starch granules extracted in rice showed an irregular shape, the starch granules in wheat were lenticular-shaped and spherical-shaped. The starch granules in maize grain were mainly polyhedral or irregular and spherical in shape. Distributions of starch granule number, volume and surface area were changed in a typical unimodal-peak curve, a triple-peak curve and a typical bimodal-peak curve, respectively, in grains of rice and maize. Distributions of starch granule number, volume and surface area in wheat grains displayed a typical unimodal-peak curve, a four-peak curve and a triple-peak curve, respectively. According to starch granule diameters, all the starch granules were classified into small, medium, and large granules in this study. The thresholds for separating the starch granules were 1.5 μm and 20.0 μm, 5.0 μm and 50.0 μm, 4.0 μm and 50.0 μm, respectively, in rice, wheat and maize. The total volume of starch granules in grains of the three cereal crops was mainly determined by the volume of medium starch granules. No significant difference was observed in the proportions of small starch granule size and medium starch granule number between superior and inferior grains of the three cereal crops. But the volume and surface area of medium starch granules were larger in superior grains than in inferior ones. The percentage of large starch granules was greater in the inferior than in the superior. Changes in the volume of medium starch granules in both superior and inferior grains were consistent with those in starch accumulation and grain weight. The results suggest that the starch granule volume is an important factor determining grain weight. Increasing the volume of medium starch granules or reducing the volume of large starch granules would increase the weight of inferior grains.