寒地粳稻氮代谢对孕穗期冷水胁迫的响应机制及外源物质的调控效应

Rice is one of the most important crops in the world, improving rice production is taking up the task of national food security. Chilling damage at booting stage seriously limits rice yield in temperate climates ,such as Heilongjiang Provence. The effect of chilling at booting stage on rice is one of the top topics in this filed, however there was few stduy about the effect of chilling at booting stage on nitrogen metabolism, especially on GABA shunt.Two Japonica rice varieties DongNong 428 and Songjing 10 with a similat growth period and different cold tolerance were used in this study. as test material.In order to reveal the response of nitrogen metabolism to cold water stress at booting stage , the key enzymes activities in nitrogen metabolism, the expression responses of key enzymes genes and the expression responses of protein in leaves; amino acids component and nitrogen content in leaves and grain were investiaged in this study. Moreover, we focusd on the panicle development, pollen activity, pollen super micro structure, dry material accumulation of grain, yield-related traits and yield, in order to study the effect of cold water stress on yield in japonica rice. In addition, the regulation of exogenous substances(γ-Aminobutyric acid, glutamic acid and calcium chloride) on nitrogen metabolism and yield under cold water stress in Japonica rice were also investigated in this study.By adjusting the concentration of exogenous substances , we can thus improve rice cold tolerance, which is meaningful guidance of Japonica rice cultivation and provide a scientific basis and foundation for the establishment of effective cultivation mode against chilling damage. This research has important theoretical significance and practical application value.

水稻是重要的粮食作物，发展水稻生产对维系国家粮食安全，尤其是口粮安全至关重要。孕穗期低温冷害是限制水稻产量提高的重要因素。关于水稻孕穗期低温冷害的研究备受学者关注，但有关氮代谢对水稻孕穗期冷水胁迫响应机制的研究，尤其是γ-氨基丁酸（GABA）支路的研究国内外未见报道。本课题拟用生育期相近、耐冷性不同的2个粳稻品种东农428、松粳10为试验材料，研究孕穗期冷水胁迫下叶片氮代谢相关酶活性、调控基因和差异蛋白表达，以及叶片和籽粒氨基酸组分、氮素含量，揭示氮代谢对冷水胁迫的响应机制，丰富水稻耐冷生理基础；研究冷水胁迫下颖花形成规律、花粉粒活性和超微结构以及籽粒干物质积累和产量构成因素，揭示冷水胁迫对寒地粳稻产量形成的影响；研究冷水胁迫下外源物质（谷氨酸、氯化钙、GABA）对寒地粳稻氮代谢及产量形成的调控效应，为有效抵御低温冷害、指导寒地粳稻生产提供理论依据。本研究具有重要的理论意义和实际应用价值。

孕穗期低温冷害是限制水稻产量提高的重要因素。关于氮代谢对水稻孕穗期冷水胁迫响应机制的研究，尤其是γ-氨基丁酸（GABA）支路的研究未见报道。本课题用耐冷性不同的粳稻品种东农428、松粳10为试验材料，研究孕穗期冷水胁迫下叶片氮代谢相关酶活性、调控基因和差异蛋白表达、叶片和籽粒氨基酸组分、氮素含量，颖花形成规律、花粉粒活性和超微结构以及籽粒干物质积累和产量构成因素，谷氨酸、氯化钙、GABA对寒地粳稻氮代谢及产量形成的调控效应。.结果发现，孕穗期冷水胁迫严重影响寒地粳稻功能叶片和籽粒氮代谢水平。籽粒全氮、蛋白氮和淀粉颗粒态结合蛋白是不同耐冷性品种响应冷水胁迫的差异产物，其含量高低可作为耐冷性鉴定的指标。冷水胁迫下东农428 中1个涉及 L-鸟氨酸合成的鸟氨酸氨基甲酰基转移酶基因显著高于松粳10。孕穗期冷水胁迫下植株吸氮量下降，促进叶片和茎鞘中氮素向籽粒转运；叶片氮光合效率下降与氮代谢关键酶活性降低有关，进而影响光合产物及氮素的积累。地上部氮素积累量的降低，导致叶面积指数和净光合速率随之下降，影响了穗的正常发育。.孕穗期冷水胁迫严重影响寒地粳稻产量形成，抑制粳稻花粉发育进程，花粉绒毡层断裂或消失；颖花及枝梗分化数减少，退化数增加，对二次枝梗和二次颖花的影响大于一次枝梗和一次颖花，对中、下部枝梗和颖花的影响大于上部。冷水胁迫下，寒地粳稻籽粒干物质积累量降低，除与籽粒干物质最大相对积累速率降低有关外，还与结实率降低、有效穗数和每穗总粒数减少有关，结实率的显著下降是导致产量降低的另一重要原因。.筛选出外源最适浓度配比为1.87mM氯化钙、2.76mM谷氨酸、4.40mMGABA。施用最适浓度配比外源物质可显著提高寒地粳稻功能叶片氮代谢水平，这一方面可使谷氨酸家族氨基酸含量显著上升，如抗逆氨基酸GABA、脯氨酸、谷氨酸等，另一方面可避免高NH4+毒害，促进功能叶片叶绿素的合成，提高光合产物生产能力，进而达到减灾保产的目的。