干旱胁迫对小麦不同品种胚乳淀粉结构和理化特性的影响

Effects of Drought Stress on Wheat Endosperm Starch Structure and Physicochemical Properties of Different Varieties

【目的】全面了解干旱胁迫对小麦不同品种胚乳淀粉组成、粒度分布、糊化特性以及晶体特性的影响,揭示小麦淀粉结构与理化特性的内在关系。【方法】2013—2015年度以小麦品种京冬8(JD8)、河农825(HN825)、冀麦585(JM585)、农大211(ND211)为试验材料,设节水灌溉(W)和旱作(D)2种处理,研究干旱胁迫对小麦胚乳淀粉结构及其理化特性的影响。【结果】干旱胁迫显著抑制了小麦胚乳淀粉的积累,但对小麦淀粉直/支比的影响不显著。小麦胚乳淀粉粒体积、表面积和数目分布均呈双峰曲线变化,干旱胁迫对淀粉粒粒度分布的影响因基因型和粒径大小的不同而存在差异,其中对粒径<5μm淀粉粒的表面积、数目分布影响最大。干旱胁迫未改变小麦胚乳淀粉的晶体类型,但显著提高了小麦淀粉的结晶度,对小麦淀粉X-衍射图谱中各尖峰强度的影响因品种和衍射角的不同而存在差异。干旱胁迫显著提高了小麦淀粉的低谷黏度和糊化温度,延长了糊化时间,但显著降低了小麦淀粉的峰值黏度和稀懈值,对终结黏度和回生值的影响存在基因型差异。相关分析表明,小麦胚乳淀粉结晶度与总淀粉和直链淀粉含量呈显著负相关,与支链淀粉呈显著正相关。总淀粉含量与峰值黏度呈显著正相关。直链淀粉含量与峰值黏度和稀懈值呈显著正相关,与糊化温度呈显著负相关。支链淀粉含量与糊化特性的相关性不显著,而淀粉直/支比仅与糊化时间呈显著负相关。小麦胚乳淀粉中粒径<5μm和<10μm的淀粉粒体积百分比与终结黏度和回生值均分别呈显著、极显著负相关,而粒径>15μm的淀粉粒与终结黏度和回生值均呈显著正相关。小麦淀粉粒体积分布与结晶度的相关性不显著。小麦淀粉糊化峰值黏度和稀懈值与结晶度分别呈极显著和显著负相关,而糊化温度与结晶度呈显著正相关。【结论】干旱胁迫改变了小麦胚乳淀粉组分、粒度分布、结晶度及其主要糊化参数。小麦胚乳淀粉结构与晶体特性和糊化特性之间均存在明显的相关性,表明干旱对小麦淀粉结构的影响,间接影响了其理化特性,因此,可以通过调节水分条件来生产一定品质的小麦。

【Objective】The objective of this experiment is to study the effects of drought stress on the composition, granule size distribution, pasting properties and crystal properties of wheat endosperm of different varieties, and reveal the intrinsic relationship between the structure and physicochemical properties of wheat starch. 【Method】The wheat cultivars Jingdong8（JD8）, Henong825（HN825）, Jimai585（JM585） and Nongda211（ND211） were used as the test materials, and irrigated and rainfed treatments were designed in research of the effects of drought stress on wheat endosperm starch structure and physicochemical properties. 【Result】Drought stress significantly inhibited the accumulation of starch in wheat endosperm, but it had no significant effect on the Am/Ap ratio of wheat starch. The granule volume, surface area and number distribution of wheat endosperm showed a bimodal curve. The effect of drought stress on starch grain size distribution of wheat endosperm was different due to the difference of genotype and grain size, in which it had a great influence on the surface area and the number distribution of starch granule size 〈5 μm. Drought stress didn’t change the crystal type of wheat endosperm starch, but significantly increased the crystallinity of starch, and the effects of drought stress on intensity of X-ray diffraction peak were different due to different cultivars and diffraction angles. Drought stress significantly increased trough viscosity and pasting temperature of starch, prolonged the pasting time, while significantly reduced the peak viscosity and breakdown, and there was a genotypic difference in final viscosity and setback. Correlation analysis showed a that the wheat endosperm starch crystallinity showed significant negative correlation with total starch and Am content, and a significant positive correlation with Ap content. The total starch content showed a significant positive correlation with peak viscosity. The Am content showed a significant positive correlation with peak viscosity and breakdown, and a negative correlation with the pasting temperature. The correlation between the Ap content and pasting parameters was not significant, while the Am/Ap ratio of wheat starch showed a significant negative correlation with the pasting time. The volume of 〈5 μm and 〈10 μm starch granule, respectively, showed a significant and an extreme significant negative correlation with final viscosity and setback, but the starch granule with diameter 〉15 μm was positively correlated with final viscosity and setback. The correlation between granule volume distribution and crystallinity of wheat was not significant. Wheat starch peak viscosity and breakdown, respectively, showed an extremely significant and significant negative correlation with crystallinity, but there was a significant positive correlation between the pasting temperature and crystallinity. 【Conclusion】Drought stress changed the wheat endosperm starch composition, granule size distribution, crystallinity and pasting parameters. There were significant correlations between wheat endosperm starch structure and physicochemical properties, indicating that the effects of drought stress on the structure of wheat starch, indirectly affected the physicochemical properties, therefore, the cultivation conditions could be adjusted to achieve the purpose of quality wheat production.