Abstract:

By choosing Medicago sativa L. ‘Gannong No.3’ as the material and simulating the existent form of two different nitrogen(NO₃^--N and NH₄⁺-N) in the soil, the effects of five kinds of nitrogen levels (0, 105, 210, 315, 420 mg·L^-1) of mixed nitrogen(NO₃^--N: NH₄⁺-N=1:1) on nitrogenase activity and ureide content of ‘Gannong No.3’ were researched. And the method of outdoor (rain-proof screenhouse) potting sand culture with nutrient solution was used(Test1); then the effects of seven kinds of different ratio of NO₃^--N and NH₄⁺-N(NO₃^--N:NH₄⁺-N equals 1/7, 1/3, 3/5, 5/5, 5/3, 3/1 and 7/1 respectively) of two different forms of nitrogen(NO₃^--N and NH₄⁺-N) under the best nitrogen concentrate, which was selected from Test 1, were studied (Test 2); and the correlation between nitrogenase activity and ureide content were analyzed. All the results indicated that the exogenous nitrogen concentration of promoting ureide content accumulation and nodule nitrogen fixation ability the most was 210 mg·L^-1; the best mixed nitrogen ratio of NO₃^--N and NH₄⁺-N was 1/3; ureide content(y) and nitrogenase activity(x) of aboveground parts in both tests were positively related (P < 0.01). This could be expressed by two kinds of highly similar models, which is y=0.0321x+0.4759(R=0.911) and y=0.0313x+0.5545(R=0.960). It provided a theoretical basis for seeking a simple method to evaluate nitrogen fixation ability.

Key words: Medicago sativa L., Nitrogen form, Ureide, Nitrogenase activity, Correlation

摘要：

以‘甘农3号’为研究材料,采用室外(防雨网室)盆栽营养液砂培法,模拟土壤中2种氮素形态(NO₃^--N和NH₄⁺-N)的存在形式,研究混合态氮(NO₃^--N:NH₄⁺-N为1:1)的5个供氮水平(0,105,210,315,420 mg·L^-1)对紫花苜蓿固氮酶活性和酰脲含量的影响并筛选出最佳氮浓度;在筛选出的最佳氮浓度下研究2种形态(NO₃^--N和NH₄⁺-N)氮的7种不同的配比NO₃^--N:NH₄⁺-N(1/7,1/3,3/5,5/5,5/3、3/1,7/1)对紫花苜蓿固氮酶活性和酰脲含量的影响;并对根瘤固氮酶活性和酰脲含量之间的相关关系进行了分析。研究表明:最能促进紫花苜蓿酰脲累积和根瘤固氮能力的外源氮浓度为210 mg·L^-1;最佳混合型态氮配比为NO₃^--N:NH₄⁺-N=1/3。2种试验处理下紫花苜蓿地上部分酰脲含量(y)与固氮酶活性(x)之间分别存在显著正相关关系(P < 0.01),可分别用y=0.0321x+0.4759(R=0.911)和y=0.0313x+0.5545(R=0.960)表示,且2模型高度相似,这为寻求生产中评估紫花苜蓿固氮能力的简便方法提供理论依据。

关键词: 紫花苜蓿, 氮素形态, 酰脲, 固氮酶活性, 相关性