结实期碳氮代谢互作对优质食味水稻品质形成的影响及其机理

With the improvement in living standard and the intensification in market competition, the rice with good taste has become soaring popular consumption in the market. The coordination and interaction of carbon and nitrogen metabolism during grain filling period can alter the starch and protein composition of the harvested products and thus improve the rice taste quality. However, little information is available on effect of carbon and nitrogen metabolism interaction during grain filling period on quality of rice with good taste. The proposed research would be conducted with representative good taste rice and set panicle nitrogen fertilizer level and artificial shading during grain filling treatments, to form rice population with different carbon and nitrogen metabolism capability during grain filling period. Then treatments of gradient type change, such as strong- carbon- metabolism- weak- nitrogen- metabolism pattern, weak- carbon- metabolism- strong- nitrogen- metabolism pattern, coordinated- carbon- nitrogen- metabolism pattern et al., would be selected to be focused on. The parameters, including leaf photosynthetic and senescence traits, grain filling dynamic traits, and carbon and nitrogen metabolites and enzyme activity of leaf and grain during grain filling period, and yield, quality (especially the taste quality), and starch and protein quality of endosperm at maturity, were determined to elucidate the synergistic interaction traits of carbon and nitrogen metabolism of plant during grain filling period, the formation law of rice taste quality and their interrelation. With grain filling process the main line and the starch and protein synthesis the core, the physiological and biochemical basis of quality (emphasis on taste quality) formation of good taste rice would be revealed, based on the plant carbon and nitrogen metabolism during grain filling period. The results would provide scientific support for the innovation of high yield and good taste rice cultivation techniques.

近年来好吃的稻米越来越受到市场欢迎。稻米食味优质与结实期植株碳氮代谢的协调互动调控可食用部位淀粉和蛋白质的平衡结合密切相关，但关于结实期植株碳氮代谢互作对优质食味水稻品质形成的影响及其机理尚不清楚。本项目拟选用代表性优质食味水稻品种为材料，通过设置氮素穗肥施用水平和结实期冠层遮光处理，塑造结实期植株碳氮代谢能力强弱差异的群体，从中选出碳强氮弱、碳弱氮强、碳氮协调等梯度型变化的处理，紧扣结实期叶片光合和衰老、籽粒灌浆动态、叶片和籽粒碳氮代谢产物及关键酶活性，成熟期水稻产量、稻米品质（重点是食味品质）、胚乳淀粉和蛋白质品质等指标，解析结实期植株碳氮代谢协同互动特点和稻米食味品质形成规律及其相互关系。以籽粒灌浆过程为主线，淀粉和蛋白质合成路径为核心，重点从结实期植株碳氮代谢这一角度揭示优质食味水稻品质（重点是食味品质）形成的生理生化基础，为优质食味水稻丰产调优栽培技术的更新提供科学依据。

稻米优质与结实期植株碳氮代谢的协调互动调控食用部淀粉和蛋白质的平衡结合密切相关。穗肥施氮量和结实期光照可通过影响水稻植株氮营养和叶片光合籽粒碳氮代谢能力产生调节作用，形成不同特征的稻米品质。本研究设置2.7、5.4和8.1 kg•667 m-2穗肥施氮量处理及结实期冠层100%和50%自然光照处理，研究优质水稻产量、品质、光合与衰老、淀粉和蛋白质代谢等特征，进而揭示在穗肥施氮量和结实期遮光的作用下水稻产量与品质对结实期碳氮代谢协同互动的应答机制。主要结果为：适宜穗肥施氮量利于水稻产量提高，结实期遮光显著降低水稻产量，且结实期遮光引起的产量下降随穗肥施氮量增加而加重。穗肥施氮量增加和结实期遮光均显著降低结实率和千粒重。在穗肥施氮量增加和结实期遮光的作用下，结实期剑叶SPAD值、过氧化物酶活性和过氧化氢酶活性均增加，丙二醛含量降低，光合速率、光合酶活性和过氧化物酶活性分别呈增加和下降。结实期籽粒淀粉代谢关键酶活性随穗肥施氮量增加而增加；除淀粉分支酶活性增加外，其他酶活性随结实期遮光而降低。穗肥施氮量增加和结实期遮光均降低了籽粒硝酸还原酶和谷氨酰胺合成酶活性，但增加了谷氨酸合成酶活性。在穗肥施氮量增加和结实期遮光的影响下，稻米淀粉含量与蛋白质含量比降低，蛋白质含量和各组分含量增加，淀粉含量降低，淀粉小淀粉粒和中淀粉粒比例、相对结晶度、膨胀势、溶解度、热焓值、消减值增加，淀粉大淀粉粒比例、峰值黏度、最终黏度降低，淀粉晶体有序度、回生焓和回生度分别为降低和增加。穗肥施氮量增加和结实期遮光均利于提高青米率、垩白度、蛋白质含量，降低整精米率、直链淀粉含量、胶稠度，提升米饭硬度，降低米饭弹性、粘性和平衡性，降低米饭食味值。因此，适量减施穗肥施氮量利于结实期遮光下部分稻米品质提升，降低直链淀粉含量特别是蛋白质含量可能是提升食味的有效途径，以期为优质水稻丰产调优栽培技术更新提供依据。