作 者 ：李文阳,闫素辉,尹燕枰,李勇,梁太波,耿庆辉,戴忠民,王振林*
期 刊 ：生态学报 2009年 29卷 1期 页码：298~306
Keywords:winter wheat (Triticum aestivum L.), shading, starch, starch granule, granule size distribution,
摘 要 ：在籽粒灌浆阶段（花后1～30 d）对小麦进行光强为自然光照45％的弱光处理，研究了小麦籽粒淀粉粒度分布和组分含量的变化。结果表明，小麦籽粒淀粉粒体积分布呈双峰曲线，峰值分别在5.1～6.1 μm和20.7～24.9 μm，两峰值间的低谷出现在9.9 μm左右。表面积分布和数目分布分别表现为双峰和单峰曲线。小麦花后弱光显著降低2.8~9.9 μm淀粉粒体积百分比，增加22.8~42.8 μm淀粉粒体积百分比。同时花后弱光显著降低<0.8 μm和2.8~9.8 μm淀粉粒表面积百分比，增加0.8~2.8 μm和>9.9 μm淀粉粒表面积百分比。可见灌浆期弱光显著降低籽粒B型（＜9.9 μm）淀粉粒体积和表面积百分比，而A型（＞9.9 μm）淀粉粒比例相对增加。与A型淀粉粒相比，B型淀粉粒对弱光的反映更敏感。小麦弱光处理籽粒淀粉及其组分含量显著低于对照，但其直/支比较对照高。相关分析表明，籽粒直/支比与2.8~9.9 μm淀粉粒体积百分比呈显著负相关，而与22.8~42.8 μm淀粉粒体积百分比呈显著正相关。花后不同阶段弱光显著增加A型淀粉粒体积百分比、降低B型淀粉粒体积百分比，其中灌浆中、后期弱光影响程度较前期大。表明，弱光条件下小麦籽粒淀粉合成底物优先供应淀粉粒的生长，而非形成更多的淀粉粒。
Abstract:Starch, the main carbohydrate in the endosperm of wheat grain, is an important determinant of the textural and processing properties of many foods. Starch is deposited in the endosperm as discrete semi-crystalline aggregates known as starch granules during grain development. Various authors have demonstrated that the starch granules in wheat grain endosperm exist in two contrasting types, a large, A- (>9.9 μm) and a little, B-type (<9.9 μm) starch granules, which are different significantly in their physical, chemical and functional properties. It was generally accepted that the starch granule size distribution had a close association with the usage in industrial food and nonfood applications. Low light intensity as a result of cloudy or rainy days, and densely planting population often occurs during the grain filling of winter wheat. However, there is little knowledge about the effect of low light intensity after anthesis on starch granule size distribution in wheat grain. The field experiments were carried out at Tai′an Experimental Station of Shandong Agricultural University in two growing seasons from October 2005 to June 2006 and from October 2006 to June 2007. Two winter wheat (Triticum aestivum L.) cultivars, SN12 and SN1391, were chosen in this study. The field was shaded by the black nets with 55% shading over the plants during grain filling (1-30 d after anthesis, SH) in this study. And the black nets were also over the wheat canopy to reduce light intensity to 10% in the early (6-9 d after anthesis, S1), middle (16-19 d after anthesis, S2) and late (26-29 d after anthesis, S3) grain filling stages. The treatments were arranged in a randomized complete design with three replications. Effect of shading during grain filling in field on starch granule size distribution and starch component content was examined in wheat grain at maturity. The results showed that volume distribution showed the typical two populations of starch granules with peak values in the ranges of 5.1-6.1 μm and 20.7-24.9 μm, respectively. The limit between the two populations was defined as the minimum of the curves that occurred at 9.9 μm. Surface area distribution of starch granules also was the two populations of starch granules, and number distribution of starch granules exhibited a single peak curve. The volume % of 2.8-9.9 μm starch granules was significantly decreased, and that of 22.8-42.8 μm starch granules was significantly increased under shading stress. The surface area % of starch granules in shading stress with the ranges of <0.8 μm and 2.8-9.9 μm were lower, and that of the ranges of 0.8-2.8 μm and >9.9 μm were higher than those of control. These observations suggest that shading stress led to a significant decline in volume % and surface area % of B-type starch granules (<9.9 μm) and increase in those of A-type starch granules (>9.9 μm), respectively. B-type starch granules were more sensitive to shading stress than A-type starch granules in wheat grain. There was significant effect of shading stress after anthesis on starch and starch component content. Shading stress remarkably reduced starch and starch component content at the maturity. However, the ratio of amylose and amylopectin of shading stress was higher than that of control in grain. The ratio of amylose to amylopectin was negatively correlated with volume % of 2.8-9.9 μm starch granules, and positively correlated with volume % of starch granules of 22.8-42.8 μm. It was found that the volume % of A-type starch granule was significantly increased and that of B-type starch granule was significantly decreased due to shading stress at different grain filling stages, especially at middle and late grain filling stages. Based on results here we consider that under dim light condition, the limited substrate for starch accumulation was mainly partitioned for growing starch granules, not for producing more starch granules.
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