Root Growth Patterns in Relation to Nitrogen Availability

根系生长模式与氮利用率的关系

• 批准号: 8806585
• 负责人: Arnold Bloom
• 金额: $ 13.5万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-07-15 至 1991-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8806585&HistoricalAwards=false
• 关键词: Root; Growth; Patterns; Relation; Nitrogen

Nitrogen is the mineral element that plants require in greatest quantity and its availability determines to a large extent the productivity of both natural and cultivated ecosystems. The two mineral forms of nitrogen accessible to plants are ammonium and nitrate. Little is known abut the relative importance of ammonium and nitrate as nitrogen sources under field conditions, in part, because of the methodological limitations. Nitrogen has no long-lived radioisotope. Use of the stable isotope 15N-the most common approach for measuring plant absorption from soils-has major disadvantages. The proposed research shall develop new field methods for studying plant nitrogen absorption utilizing methylamine, a chemical analog for ammonium, and chlorate, a chemical analog for nitrate. These analogs have several advantages. They are not readily metabolized in the soil. They can be used at low concentrations because they have long-lived, radioactive forms, 14C-methylamine and 36Cl-chlorate. Moreover, use of the radioactive forms can separate ammonium from nitrate absorption. The objective is to design a procedure which uses only small amounts of radioactive compounds and ensures that virtually no radioactive material is left in the field. Field experiments using these techniques will access seasonal and spatial changes in the availability of ammonium and nitrate. The distribution of tomato roots through the soil should indicate whether roots develop special branching patterns to optimize the absorption of ammonium or nitrate. Tomato mutants that have diminished abilities to absorb ammonium or nitrate or unusual root branching patterns have been isolated. Differences among the nitrogen accumulation in these mutants and that in normal tomatoes should reflect the relative importance of plant physiological mechanisms and root morphology on ammonium or nitrate absorption from soils. This research brings together innovative techniques and unique genetic material to examine nitrogen acquisition under realistic conditions. This information should stimulate the development of cultivars and agricultural practices that increase the efficiency of nitrogen fertilizer use. Because the production of nitrogen fertilizer expends from 1/3 to 1/2 of the total energy inputs in modern agriculture, increased nitrogen fertilizer efficiency would dramatically reduce the energy requirements of agriculture.

氮是植物所需的最大量的矿物质元素，其有效性在很大程度上决定了自然生态系统和栽培生态系统的生产力。植物可利用的两种矿物质形态的氮是铵和硝酸盐。在田间条件下，由于方法的限制，人们对铵和硝酸盐作为氮源的相对重要性知之甚少。氮没有长寿的放射性同位素。使用稳定同位素15N--测量植物从土壤中吸收的最常见方法--有很大的缺点。这项拟议的研究将开发利用甲胺和氯酸盐研究植物氮素吸收的新田间方法。甲胺是一种氨的化学类似物，氯酸盐是硝酸盐的化学类似物。这些类比有几个优点。它们在土壤中不易代谢。它们可以在低浓度下使用，因为它们具有长寿命的放射性形式，14C-甲胺和36Cl-氯酸盐。此外，使用放射性形式可以将铵从硝酸盐吸收中分离出来。其目标是设计一种只使用少量放射性化合物的程序，并确保几乎没有放射性物质留在现场。使用这些技术的田间试验将获得铵和硝酸盐有效性的季节和空间变化。番茄根部在土壤中的分布应该表明，根部是否形成特殊的分枝模式，以优化对铵或硝酸盐的吸收。已经分离出吸收铵或硝酸盐能力减弱或不寻常的根分枝模式的番茄突变体。这些突变体与普通番茄氮素积累的差异反映了植物生理机制和根系形态对土壤中氨氮或硝酸盐吸收的相对重要性。这项研究结合了创新技术和独特的遗传材料来检查现实条件下的氮素获取。这些信息应该刺激品种和农业实践的发展，从而提高氮肥的使用效率。在现代农业中，由于氮肥生产占总能量投入的1/3到1/2，氮肥利用率的提高将大大降低农业对能源的需求。