【作者】 曹云；

【导师】 沈其荣；

【作者基本信息】 南京农业大学 ， 植物营养学， 2006， 硕士

【摘要】 铵态氮和硝态氮是植物生长过程中主要的两种矿质氮源。由于淹水条件下硝化作用被强烈抑制，NH₄⁺成为水稻田土壤N的主要存在形式，因此前人对水稻N营养的研究主要侧重在NH₄⁺营养而忽略了对NO₃^-营养的研究。但值得注意的是，水稻根系能分泌O₂，这些O₂能被土壤硝化微生物利用，将NH₄⁺氧化为NO₃^-，因此水稻根际中存在着一定的NO₃^-。越来越多的研究表明，水稻对两种形态的N都可以吸收和利用。但是水稻为什么存在对硝态氮营养的基因型差异?水稻根系吸收NO₃^-以后，如何在体内同化的?本研究在水培条件下，以不同水稻品种为材料，从氮素同化的角度分析了硝态氮对不同水稻品种生长的影响；增硝营养对不同水稻品种氮代谢关键酶（硝酸还原酶以及谷氨酰胺合成酶）活性及其基因表达量的影响。试图通过以上的内容揭示不同水稻品种同化利用硝态氮的生理与分子生理机制。 本文首先研究了在1mmol.L^-1 NO₃^-培养下，4个品种水稻（汕优63（杂交籼稻H-I）、扬稻6号（常规籼稻I）、泗优917（杂交粳稻H-J）、农垦57（常规粳稻J））生长量及其水稻苗期硝酸还原酶活性（NRA）和谷氨酰胺合成酶活性（GSA）。结果表明，培养28d后，籼稻与粳稻之间生长差异显著。其中，扬稻6号生长最优，农垦57最差，扬稻总氮含量显著高于农垦，说明扬稻对硝态氮的吸收利用效率高于农垦。籼稻体内的NRA显著高于粳稻，说明籼稻对硝态氮的同化能力优于粳稻。 不仅籼稻和粳稻之间硝态氮利用能力存在差异，不同粳稻品种之间也存在氮效率差异。因此，本文在大田试验的基础上筛选了不同氮效率水稻品种，分别为南光和云粳，并以它们为材料，研究了增硝营养（NH₄⁺：NO₃^-比例为100：0和50：50）对两种不同的基因型水稻南光和云粳苗期生长、硝酸还原酶（NR）活性及基因表达量、谷氨酰胺合成酶活性及基因表达量的影响。结果表明：不同基因型水稻在增NO₃^-营养下生物量、氮素含量、氮积累量增幅不一，南光增幅大于云粳。NO₃^-的存在增强了水稻硝酸还原酶的活力和NR基因OsNia1、OsNia2的表达。不同基因在水稻幼苗中的表达量有差异，两个品种OsNia2的相对表达量均高于OsNia1。就品而言，无论叶片还是根系，增硝后南光OsNia2 mRNA表达量都高于云粳；南光叶片OsNia1 mRNA表达量也较云粳叶片高。增硝营养提高了水稻NR基因的表达进而增加了NR活性，促进了水稻NO₃^-的同化并利用。更多还原

【Abstract】 Nitrate and ammonium are the predominant inorganic N forms in soil thatutilized by plants. Since nitrification is strongly inhibited and ammonium becomes the major form of N in paddy soil, previousstudies concern more ammonium than nitrate nutrition of rice plants. Although NH₄⁺ is usually considered to be the preferred nitrogen source of rice （Oryza sativa L.）, the roots are actually exposed to a mixed nutrition of NH₄⁺ and NO₃^-due to the excretion of O₂ by the roots and subsequent nitrification in rhizosphere. But what are the reasons behind the difference in their capability of utilizing nitrate among rice genotypes? How is nitrate be metabolised once absorbed by rice roots? To answer these questions,this thesis studied the effects of NO₃^-on N utilization by rice plants at molecular physiological level. Hydroponic experiments were conducted to study the effect of nitrate on the growth, the changes in enzyme activities and transcript levels of nitrate reductase and glutamine synthetase by different rice cultivars.Firstly, four rice cultivars, Indica, Japonica and two hybrid cultivars were grown in solution culture containing 1 mmol.L^-1 NO₃^- and their growth and utilization of nitrate were compared. Indica produced the greatest biomass while Japonica the lowest growth among the four cultivars in 1 mmol.L^-1 NO₃^-. Indica rice had higher nitrate reductase activity （NRA） and glutamine synthetase activity （GSA） than Japonica rice in 1 mmol.L^-1NO₃^- , suggesting that Indica rice had a greater ability to utilize nitrate than Japonica.The difference in nitrogen recovery is not only found between Indica and Japonica rice, but also within different Japonica rice cultivars. Therefore, we selected two rice cultivars of different NUE based on the results of field experiments. Solution culture experiments were conducted to study the influence of nitrate （NO₃^-） on the activities of nitrate reductase （NR） and glutamine synthetase （GS） and transcript levels of two NR genes, i.e. OsNial, OsNia2, two cytosolic GS1 genes, i.e. OsGln1;1更多还原