叶菜的硝态氮临界含量和耐铵能力

More and more attention has been paid to nitrate accumulation in vegetables for its detrimental impact on human health. A great number of cultivation experiments in greenhouse and field trails on vegetable lands were conducted, with different vegetable species and cultivars, to study the critical nitrate concentration (CNC) of leafy vegetables and its effecting factors. Obtained results showed that the nitrate accumulation was a very common phenomenon for all dryland crops, N fertilizers added to soil was the major source for the accumulated nitrate, the unbalance between nitrate absorption and reduction caused by over-fertilization of N was the principle cause for nitrate accumulation, and the non-coordination between absorption and growth accelerated the accumulation process. Petiole is the optimum part for determining the CNC among different vegetable organs and the CNC had been determined for 3 vegetables and 7 spinach varieties. Results indicated that the CNC was different with vegetable species and varieties, negatively related with the ratios of leave blades to shoots as well as the ratio increasing degrees with the increase of N rates. The CNC was also affected by water metabolism, and vegetables with higher CNC always showed higher water use efficiency. The ratio of in vivo to in vitro nitrate reductase activity (NRA) was negatively correlated with the CNC between different spinach varieties. The size of nitrate metabolic pool and nitrate distribution between metabolic and storage pool in plant cell was a key factor affecting the CNC. Vegetable with larger metabolic pool and more nitrates being distributed in that, always has lower CNC. Besides the work above, ammonium tolerance capacity, nitrate pollution in vegetables and its regulation, nutrient-supplying capacity in vegetable lands had also been investigated. Research in vegetable nutrition has always been a weak part in our country, and achievements obtained by this project will play an important role in improving the theoretical level of vegetable nitrogen nutrition in plant nutrition field.

针对叶菜硝态氮累积严重危害人类健康，以累积量高的菠菜、小白菜、莴笋为供试材料，通过温室土培、砂培和蛭石培养试验，从植物的营养生理学角度研究蔬菜正常生长时体内的硝态氮临界含量和耐氨能力。以此为基础，进行土培和田间试验，确定合理的施氮指标和可行的调控指标。为指导蔬菜合理施用氮肥，在不影响产量的前提下，提高品质提供理论依据。.

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