南方水稻产量与品质形成对弱光和低温复合胁迫的响应机制

In recent years, the sunshine hours and the total amount of radiation at the late stages of rice in southern China have been decreasing constantly, and in particular, the extreme cloudy, rainy and few sunshine weather accompanied with low temperature occurs frequently, resulting in the more serious weak light and low temperature combined stresses, which have been the key environmental factors restricting the rice yield and quality improvement in southern China. So the different weak light and low temperature combined stress treatments during heeding and grain filling of rice （1-7d、8-14d、15-21d、22-28d、29-35d after heading) were set to clarify the effect of weak light and low temperature combined stress on the grain yield, yield compoments and rice quality chariacteristics and reveal the dynamic changes of the distribution of photosynthetic production, photosynthetic physiology and physiological characteristics of aging, fine structure of starch(the development of amyloplast in endosperm, morphology and distribution of starch granule, the crystal structure and chain length distribution of starch) and starch-sugar metabolizing enzymes (AGP, SSS, SBE, SS and SPS) activities. And the relationship between the dynamic changes of these parameters and grain yield and rice quality formation will be clarified, and then we try to reveal the response mechanism of grain yield and rice quality formation to weak light and low temperature combined stress in south China, which will provide theoretical and technical support for high yield and good quality in rice stress-resistance cultivation under the condition of climate change in future.

近年来，我国南方水稻生育后期日照时数和总辐射量不断减少，极端阴雨寡照伴随低温天气发生频率明显增加，造成了较严重的弱光和低温复合胁迫，制约了南方水稻产量和品质的提升。本项目在水稻抽穗灌浆期设置不同阶段（穗后1-7d、8-14d、15-21d、22-28d、29-35d）弱光和低温复合胁迫处理，研明弱光和低温复合胁迫对水稻产量结构和品质特征的影响，揭示水稻光合物质生产与分配、光合生理和衰老生理特征、淀粉精细结构（胚乳淀粉体发育、淀粉粒形态和分布、淀粉晶体结构、链长分布等）及淀粉与糖代谢相关酶（AGP、SSS、SBE、SS和SPS）活性等的动态变化特征，阐明籽粒产量及品质形成与这些参数动态变化的关系，进而揭示南方水稻产量及品质形成对弱光和低温复合胁迫的响应机制，为未来气候变化条件下水稻高产优质抗逆栽培提供理论与技术支撑。

近年来，南方水稻抽穗灌浆期低温寡照天气发生频率明显增加，造成了较严重的弱光和低温复合胁迫，制约了南方水稻产量和品质的提升。本研究在水稻穗后不同时间段(1-7 d、8-14 d、15-21 d、22-28 d、29-35 d)设置弱光低温复合胁迫(LW)、单一弱光(WN)、单一低温处理(LN)和常温常光(NN) 4个处理，研究弱光低温复合胁迫对水稻产量、光合生理特性、稻米品质、淀粉合成酶活性与淀粉理化特性等的影响，进而揭示南方水稻产量及品质形成对弱光和低温复合胁迫的响应机制，为水稻优质高产抗逆栽培提供理论支撑。主要结果如下：.（1）穗后不同阶段弱光和低温复合胁迫极显著降低水稻结实率，尤其二次枝梗结实率，穗后14d内显著降低千粒重，进而极显著或显著降低产量。穗后21 d内，复合胁迫降低强势粒的最大灌浆速率、平均灌浆速率，而穗后21 d后，对弱势粒影响较大。（2）胁迫导致单茎穗重、单茎总干重及氮素积累量有所降低，叶片光合速率以及SPAD值下降，表现为LW<LN<NW<NN。复合胁迫降低了叶片POD、CAT活性， SOD活性先增加后下降，叶片MDA含量增加，随着时间的推移，差异逐渐减小。（3）复合及单一胁迫均造成淀粉合成相关酶AGPase、SSS、GBSS活性下降，DBE与SBE酶活性提高，以复合胁迫影响最大。（4）低温弱光复合胁迫使稻米加工品质、外观品质、蒸煮食味品质及RVA谱特征值不同程度变差，以穗后21 d内影响较大。低温弱光复合胁迫下淀粉颗粒发育不充实，淀粉表面不平滑，棱角不分明（以穗后21d内影响较大）。淀粉大颗粒增多，淀粉晶体结构不变，相对结晶度上升，淀粉的表层有序度上升，峰值强度减小，片层距离变大。低温弱光复合胁迫增加了支链淀粉含量，降低支链淀粉短链所占比例，提高长链所占比例，提高了胶凝热焓值、回生热焓值以及回生度，使淀粉容易老化，以穗后21 d 内影响较大。