【作者】 陈巍；

【导师】 沈其荣；

【作者基本信息】 南京农业大学 ， 植物营养学， 2005， 博士

【摘要】 过去的研究表明,在营养液中适当的降低硝态氮浓度,增加一定量的铵态氮不仅能显著提高作物生物量,也能显著降低叶菜体内硝酸盐累积量,提高叶菜品质。因此,在蔬菜地上施用铵态氮和硝化抑制剂是一项有益于降低硝态氮的环境流失风险、增加农民经济收入和改善人体健康的氮肥管理措施。然而,有关增铵营养对叶菜生长及其品质影响的机理仍知之不多,本博士论文采用水培条件,从植物营养和植物生理生化的角度来探讨增铵营养对小白菜生长的影响规律及适当增铵增产的机理、增铵对小白菜叶片扩展及叶绿素含量的影响规律及机理、增铵对小白菜硝酸盐含量的影响规律及降低硝酸盐含量的机理、不同品种小白菜生长及硝酸盐累积差异机理、硝态氮在小白菜体内器官及亚细胞水平的累积、调配及再利用机理等方面进行了较深入的研究。取得了如下结果: 无论在5mmol L^-1等氮条件下,还是在5mmol L^-1等硝条件下加大营养液中铵态氮浓度,小白菜生物量及叶面积均先增大后变小,营养液中添加一定量的铵态氮能提高作物生物量和促进叶片扩展。在5mmol L^-1等氮条件下,以1.25mmol L^-1的铵态氮取代硝态氮,小白菜生物量和叶面积均增加了50%;在5mmol L^-1等条件下,适当添加一定量的铵态氮(2.5 mmol L^-1)小白菜生物量和叶面积分别增加39.6%和16.3%。小白菜生物量的增加及叶面积的形成受NO₃^--N/Nh₄⁺-N比例的影响大于总氮的浓度。 5mmol L^-1等氮条件下加大营养中NH₄⁺-N的比例显著降低小白菜体内硝酸盐含量,提高叶片叶绿素SPAD值以及游离铵和含碳量。在NO₃^--N:NH₄⁺-N为3.75:1.25(mmol L^-1)时,小白菜的生物量、叶面积、含氮量、总氮及总碳累积量均最大。说明3.75:1.25(mmol L^-1)的NO₃^--N/NH₄⁺-N比最有利于小白菜总氮吸收、CO₂固定和产量的形成。 5 mmol L^-1等氮条件下,小白菜叶片可溶性蛋白含量与营养液中铵态氮浓度呈显更多还原

【Abstract】 Previous reports showed that the yield and quality of vegetables can be significantly increased by properly increasing ammonium concentration in the nutrient solution. Thus, enhancing the percentage of ammonium nitrogen in fertilizer application in vegetable production is a potential nitrogen management beneficial to the reduction of environmental risk of nitrate loss, the increase of profit of farmers and the promotion of human health. However, the mechanisms of the effect of enhanced proportion of ammonium on vegetable growth and food quality is little known till now. This thesis for doctor degree is aimed to study the related mechanisms from the view point of plant nutrition and plant physio-biochemistry. Hydroponic experiments were conducted in the greenhouse, Nanjing Agricultural University, P. R. China. Nitrate and ammonium uptake, nitrate reductase activity （NRA）, chloroplast protein content, cytokinins content, active iron and total iron contents and leaf areas, et al, were measured. Results obtained were as follows.The biomass and leaf area were mainly influenced by the ratios of NO₃^--N/NH₄⁺-N, other than total nitrogen concentration. Increasing ammonium concentration in the nutrient solution could increase both the biomass and leaf area first then decreased in either the 5 mmol L^-1 total nitrogen solution or 5 mmol L^-1 nitrate solution. As the total nitrogen concentration of the medium solution was fixed at 5 mmol L^-1, the replacement of 1.25 mmol L^-1 nitrate by ammonium increased both the biomass and leaf area by 50%. While properly added some ammonium to the 5 mmol L^-1 nitrate nutrient solution, biomass and leaf area increased by 39.6% and 16.3%, respectively.Ammonium was beneficial to the synthesis of chlorophyll and accumulation of carbon in the plants. The increasing of NH₄⁺-N ratios in the medium solution when the total nitrogen concentration was fixed at 5 mmol L^-1 increased chlorophyll SPAD readings, ammonium （free ammonium） and carbon content., The biomass, leaf area, carbon content, total nitrogen and carbon accumulation were the highest at the ratio of NO₃^--N/NH₄⁺-N, 3.75:1.25 （mmol L^-1） suggesting that 3.75:1.25（mmol L^-1） of NO₃^--N/NH₄⁺-N ratio was the best for the nitrogen uptake, CO₂ fixation and yield formation.Partial replacement of nitrate by ammonium was beneficial to soluble protein accumulation. Significant positive relationships existed between leaf soluble protein content and chlorophyll SPAD readings and ammonium concentration in the nutrient solution when the total nitrogen concentration was 5 mmol L^-1.Chlorophyll SPAD readings, active iron content and chloroplast protein content were all significantly related （p<0.05） with ammonium concentration in the nutrition solution when the nitrate concentration was fixed as 5 mmol L^-1, with the coefficients being 0.914, 0.954 and 0.964. The coefficients of active iron content with chlorophyll SPAD readings and chloroplast protein content were 0.841 and 0.912 respectively. There was no significant relationship between chlorophyll SPAD readings and leaf area. The increased chlorophyll content was not the condensed effect caused by leaf shrink, but the ammonium-promoted chlorophyll synthesis, which was caused by reusage of total iron in the plants, thus increasing active iron content in leaf blades and chloroplast protein content.At 5 mmol L^-1 total nitrogen solution, partial relacement of nitrate by ammonium significantly increased cytokinin content. There was a significant relationship between leaf area and cytokinin content （r =0.970,p<0.05）. At the 5 mmol L^-1 total nitrogen and 5 mmol L^-1 nitrate solution, the coefficients of the leaf area of the fully expanded top leaf blade and biomass were 0.966 and 0.941, which were both significant at p<0.01.Genetic differences existed in nitrogen nutrition and biomass.The decreasing order of Shanghaiqing> Luxingqincai>Kangre 605> Liangbaiye 1 was found in the items of biomass, chlorophyll SPAD readings, carbon contents, total carbon and nitrogenaccumulation, whi更多还原