灌浆结实期高温与干旱对水稻胚乳淀粉理化性状的影响及其生理机制

High temperature and drought stress are two key environment factors that affect rice yield and quality. Starch is the main rice endosperm storage material and its content and physicochemical properties determined the rice grain weight and quality. Yet the effect of high temperature and drought stress in the grain-filling stage on physical and chemical properties of rice endosperm starch and its mechanism remanded unclear. This project will study representative rice cultivars in grain-filling stage under high temperature ,drought stress, and high temperature combined with drought stress of (1) the structure of the rice endosperm starch (the starch components ratio , the average chain length, branching degree, the crystal type , the crystallization degree) change and its relationship with yield and quality formed.(2) the endosperm starch metabolism pathway key enzyme (starch synthase, starch branching enzyme, starch debranching enzyme) activity, related gene expression levels and their relationship with the endosperm and starch structure; (3) mechanism of reduced impact of external chemical control and nitrogen fertilizer application on the yield and quality of rice. Through this research project we intended to clarify the relationship and mechanism of rice endosperm starch physicochemical properties and quality formation under drought stress and high temperature in the grain-filling stage to propose cultivation techniques to improve rice quality by regulating the starch physicochemical characteristics, which will provide a theoretical basis and practical guidance for high yield and quality of rice resistant inverse cultivation and breeding.

高温和干旱是影响水稻产量和品质的两个重要环境因子。淀粉是水稻胚乳中的主要储藏物质，其含量和理化性状决定了水稻的粒重和品质。但有关灌浆期高温干旱胁迫对水稻胚乳淀粉理化性状的影响及其机理尚不清楚。本项目以胚乳直链淀粉含量有明显差异的6个水稻品种为材料，在灌浆结实期设置高温、干旱和高温干旱复合胁迫等处理，研究（1）胚乳淀粉结构（淀粉比例组分、平均链长、分支化度、晶体类型、结晶度）的变化特点及其与产量和品质形成的关系；（2）淀粉代谢途径关键酶（淀粉合酶、淀粉分支酶、淀粉去分支酶等）活性、相关基因表达量的变化及其与淀粉结构的关系；（3）外源化控与氮肥运筹对减轻高温与干旱对产量和稻米品质影响的机理。通过本项目研究以期阐明在灌浆期高温干旱胁迫下水稻胚乳淀粉理化性状的变化特征及其与品质形成的关系和机理，提出通过调控淀粉理化性状改善稻米品质的栽培技术，为水稻优质高产抗逆栽培和育种提供理论依据和实践指导。

温度和水分是影响水稻生长和发育最重要的生态因子。随着全球温室效应的增加，高温和干旱已成为严重危害水稻生产的两种主要逆境。本项目研究了水稻高温干旱胁迫下淀粉理化性状的变化特征及其与产量和品质形成的关系，减轻高温与干旱对淀粉理化性状及稻米品质影响的调控途径，我们的结果：（1）探明了高温和干旱对水稻淀粉理化特性的影响。干旱提高了直链淀粉含量和中粒淀粉比例，改善了淀粉粒的表面均匀性，降低了淀粉的相对结晶度、膨胀势、消减值和糊化焓。高温降低了直链淀粉含量和精米率，增加了垩白米率、大粒淀粉和淀粉颗粒的表面不均匀性，从而使淀粉颗粒的相对结晶度、膨胀势、消减值和糊化焓增加。高温干旱复合胁迫也有类似的结果，但幅度较小，说明当高温和干旱同时存在时，对水稻淀粉结构和理化特性有拮抗作用。（2）揭示了高温、干旱和高温干旱复合胁迫对水稻籽粒灌浆的影响及其分子机制。干旱促进弱势粒淀粉合成相关酶活性和基因表达，通过促进淀粉合成和积累，提高了籽粒灌浆速率和粒重。但高温和高温干旱复合胁迫下弱势粒淀粉合成相关酶活性和基因表达的降低，导致籽粒灌浆速率和粒重的降低。（3）明确了水稻在灌浆结实期高温和干旱下，适量增施氮肥可以使淀粉排列更加紧密，有利于提高淀粉表层有序度，改善稻米结构特性。高温和干旱下适量增施氮肥还可以使产量增加、稻米的糊化特性和食味品质变优。（4）阐明了采用轻干湿交替灌溉可以减轻抽穗灌浆期高温对稻米品质和淀粉精细结构带来的不利影响。研究结果对水稻优质高产抗逆栽培和育种有指导意义。