速生桉与降香黄檀种间氮素转移行为及根系互作机制

As one of the necessary mineral elements needed by plant Nitrogen plays an important role during the whole process of crop's life. The uptaking mechanism of N has been attacked great attention in reach field of plant nutrition. With worse environment pollution caused by unreasonable fertilization, it urgently needs to find out the right way to improve the potential sequestration and utilization efficiency of N by biological means such as varietal selection and suitable cultivation pattern. Base on the previous researches, this contribution will explore the nutrient's changes in soil and plant, N's allocation and accumulation and the relationshp between N and plant productivity in Eucalyptus pure forest and in Dalbergia odorifera and Eucalyptus mixed forest. At the same time, interspecific N sequestration, absorption, utilization and transfer and root interaction between the two species will be studied using the techniques of root separation, isotope tracer and leaf stalk injection in pot-cultured simulation experiments. To clarify the interactions effect between eucalyptus and leguminous species may improve our knowledge on the mechanism of nitrogen's uptaking and reveal the way of nitrogen fixation and transfer and its behavior mechanism in mixed forest. It is expected to provide a scientific basis for the improvement of eucalyptus plantation nutrient regulation and fertilization strategy, for the optimization of eucalyptus mixed cultivation system, for the utilization efficiency of resource and for the promotion of eucalyptus artificial forests under sustainable management systems.

氮素是植物生长发育过程中必需的营养元素之一, 植物吸收氮素的机制一直是植物营养领域高度重视的研究内容，当前不合理施肥导致的环境污染问题越发严重，如何通过一些生物途径提高植物固氮潜力和氮素利用效率是目前迫切需要解决的科学问题。本课题在前期研究基础上，对速生桉和降香黄檀混交林与桉树纯林中的土壤及植物的养分变化、氮素积累及分配、氮素与生产力的相互关系等进行分析，并进行盆栽可控模拟试验，采用根系分隔技术、同位素示踪土壤标记和叶柄注射技术，探讨速生桉和降香黄檀种间氮素的固定、转化、利用、迁移移及根系之间的相互作用；阐明桉树与豆科树种互作效应提高氮素利用效率的机理；揭示混交体系的固氮作用、氮素转移途径及其行为机制；为改善桉树人工林的养分调控与施肥策略，优化桉树混交林培育体系，提高生产力和资源利用效率，促进桉树人工林可持续经营提供科学依据。

氮素是植物生长发育过程中必需的营养元素之一, 植物吸收氮素的机制一直是植物营养领域高度重视的研究内容，如何通过一些生物途径提高植物固氮潜力和氮素利用效率是目前迫切需要解决的科学问题。本课题对速生桉和降香黄檀混交林与桉树纯林中的土壤及植物的氮素积累及分配、氮素与生产力的相互关系等进行分析，并进行盆栽可控模拟试验，采用根系分隔技术、同位素示踪土壤标记和叶片标记技术，探讨速生桉和降香黄檀种间氮素的固定、转化、利用、迁移及根系之间的相互作用；阐明桉树与豆科树种互作效应提高氮素利用效率的机理；揭示混交体系的固氮作用、氮素转移途径及其行为机制；为改善桉树人工林的养分调控与施肥策略，优化桉树混交林培育体系，提高生产力和资源利用效率，促进桉树人工林可持续经营提供科学依据。主要研究结论如下：. （1）不同氮素水平和根系分隔模式对植株生长均有影响，在同一根系分隔模式下，尾巨桉和降香黄檀的幼苗地径、苗高、根系及生物量等生长指标随氮素水平的增加而增加，且指标差异均达显著水平（P＜0.05）。. （2）在同一根系分隔模式下，随着氮素水平的增加，尾巨桉和降香黄檀叶片的绿素含量、光合作用及氮素同化酶活性提高；混交对尾巨桉生理指标起促进作用，但抑制降香黄檀该作用。. （3）在同一氮素水平条件下，混交增加尾巨桉氮素含量，降低降香黄檀氮素含量。利用15N稀释法验证得出氮素由降香黄檀向尾巨桉转移；利用15N叶片标记法证实氮素存在双向转移现象，净转移方向由降香黄檀向尾巨桉转移。. （4）通过根系互作蛋白差异分析，互作根系蛋白主要通过对植株合成与代谢蛋白表达，混交增强了尾巨桉根系蛋白合成代谢，从而促进了降香黄檀代谢功能。. （5）大田试验表明，尾巨桉与降香黄檀混交林能改善土壤营养条件，提高氮素利用效率，增强土壤微生物功能，进而调控尾巨桉生长环境，促进尾巨桉生理代谢功能及生长。