引起套作大豆碳氮代谢失调的关键酶及基因表达分析研究

With the increase of world population, the demand of food is ever increasing. It has been playing an increasing important role in increasing the multiple crop index of land, high utilization efficiency of land for the development of grain production by means of intercropping facilitation. Wheat/corn/soybean relay strip intercropping system is popular in South China. The rapid promotion and development of this system, with the development of soybean grain production, has effectively relieved supply and demand balance of soybean in China. Here in this system, due to unwanted excessive precipitation and excessive application of nitrogen, soybean usually grows prosperously at flowering and pod stages, at expense of reproductive growth of soybean. This excessive vegetative growth delays maturity and harvest, increases flower and fruit abortion, intensifies shading of the lower canopy, leads to foliar diseases and lodging, ultimately affects the soybean yield and quality. In the previous study, we found C/N imbalance exists in those excessive vegetative growth soybeans, their nitrogen metabolism is vigorous, nitrogen compounds accumulates largely in their vegetative organs, rather than transfer to grains or pods, nitrogen utilization efficiency is low in these plants, largely affecting grain yields. Thus we try to treat relay strip intercropping soybean at different nitrogen levels, to make sure the changing pattern of C/N ratio at different growth stages and analysis the relationship between C/N ratio and crop production, to understand the regulation rule of metabolic enzyme changes and analysis gene expression of C/N related genes. We aim at findng the role of C/N in responding to different nitrogen levels and regulation soybean's growth, C/N involved physiological and biochemical mechanism and gene expression in excessive vegetative growth. Its findings helps for revealing the molecular mechanism of the C / N in the regulation of plant growth and development, have important scientific significance in helping the improvement of soybean yields. It also has an important guiding significance for scientific fertilization and nitrogen-resistant varieties breeding in relay strip intercropping system. In addition, it provides academic reference for studying the excessive vegetative growth mechanism of other plants.

随着世界人口的不断增加，全球面临着巨大的粮食危机。利用间套作栽培是提高土地利用率、增加粮食播种面积和产量的关键。南方间套作大豆的迅速推广与发展，有效缓解了我国大豆供需矛盾，增加了大豆储备。生产上，由于季节性降水以及氮肥过量施用使得套作大豆易旺长，植株C/N比例失调，茎叶氮代谢旺盛，含氮化合物多而向籽粒库运转少，植株氮素利用率低，限制大豆产量的提高。本课题通过研究套作条件下不同氮肥水平下研究旺长植株的C/N值的变化规律，分析其变化背后的代谢酶调控规律及基因表达，探明套作大豆C/N在响应氮肥和调控植株旺长的生理生化及基因表达机制，其研究结果对于揭示C/N在调控作物生长发育的分子机制，提高间作套种条件下作物产量方面，具有重大的科学意义；也对科学施肥和耐水肥品种选用也有重要的指导意义；同时对其他作物研究旺长产生机制也有学术借鉴意义。

随着世界人口的不断增加，全球面临着巨大的粮食危机。利用间套作栽培是提高土地利用率、增加粮食播种面积和产量的关键。南方间套作大豆的迅速推广与发展，有效缓解了我国大豆供需矛盾，增加了大豆储备。生产商，由于季节性降水及氮肥过量施用使得套作大豆易旺长，植株C/N比例失调，茎叶氮代谢旺盛，含氮化合物多而向籽粒运转少，植株氮素利用率低，限制了大豆产量的提高。为研究套作条件下不同氮肥水平下旺长植株的C/N变化规律，本研究通过选用高水肥下易旺长品种“贡选1号”于净作和套作模式下，研究不同氮肥水平对大豆植株氮素营养变化及碳、氮代谢的影响。结果表明，施氮后植株株高、茎粗、第一节间长、地上部干物重、伤流量、根系伤流中硝态氮、伤流氨基酸总量、伤流氨基酸与硝态氮比值、地上部营养器官（叶片、叶柄、茎秆）中硝态氮、总糖、全氮含量、叶片氨基酸总量、可溶性糖、NR活性、GS活性均升高，而伤流中铵态氮、铵态氮/硝态氮比值、叶片中氨基酸总量/硝态氮含量降低；套作遮荫后株高、第一节间长、伤流液含量、伤流硝态氮、伤流氨基酸总量、地上部硝态氮、茎秆及叶柄铵态氮、叶片氨基酸总量、叶片氨基酸总量/硝态氮比值、叶片可溶性糖/可溶性蛋白升高，而伤流中铵态氮、铵态氮/硝态氮比值、叶片中氨基酸总量/硝态氮含量、叶片铵态氮、地上部营养器官（叶片、叶柄、茎秆）总糖、叶片总糖/总氮比值、NR活性、GS活性降低；净作条件下，高氮（180 Nkg•hm-2）易造成植株总糖含量降低，全氮含量升高，总糖/总氮比值降低，淀粉降低，可溶性糖/可溶性蛋白降低，地上部干物重降低；而高氮（180 Nkg•hm-2）套作遮荫后，叶片总糖增加，叶柄全氮减小，总糖/全氮和可溶性糖/可溶性蛋白的值、地上部干物重显著增加。综上所述，高氮导致植株营养生长过旺，造成大豆C/N失调而不利于大豆生产，然而套作能适当调控氮代谢，增强根系氮素营养，提高C/N值，从而一定程度上调控植株营养生长和生殖生长。