木本植物氮素内循环研究综述

Review on Internal Cycling of Nitrogen in Woody Plants

木本植物通过N内循环机制来适应有限的N供给,从而保持较高的生产力。文中从N内循环的过程、研究方法、受控因素等方面进行了综述:其过程包括休眠期N回流及翌年春季N再利用2个阶段,贮藏蛋白、精氨酸是休眠期N贮存的主要物质,谷氨酰胺是再利用阶段的主要运输载体;其研究方法主要有3种,即净余法局限于盆栽试验,N流量法通过测定不同时期树液中的N含量以及含N物质的组分来估测大树的N循环情况,同位素标记法是最常见的研究方法;树种、年龄、土壤肥力、土壤水分及大气CO_2浓度等是影响N内循环的重要因素。针对目前研究中存在的问题及有待深入研究的内容进行了评述和展望,以期为植物N内循环理论与应用研究提供借鉴。

Woody plants can keep high productivity through internal nitrogen cycling to adapt to limited nitrogen supply, i. e. , seasonal tree-internal nitrogen cycling. This paper reviewed the process of internal N cycling of, the research methods and the factors. The internal cycling of N includes two parts, i.e. , nitrogen retranslocation during the process of leaf senescence in the fall, and nitrogen remobilization in the following spring. Released N as vegetative storage proteins （VSP） and Arg are stored matters in the process of N retranslocation, while Gln is the transport carrier during the process of N remobilization. Three methods were used to study the internal cycling of N. First one is net approach, which can be only used in pot experiments. Second one is estimation of annual N-flux of full-grown trees by quantifying nitrate concentrations in xylem samples. The last one, labled 15N, is the most widely used method. There are several important factors influencing seasonal tree-internal nitrogen cycling, including tree species, the age of trees, soil fertility, water conditions of soil and atmospheric CO2 concentration. In addition, this article provides a valuable reference to facilitate future studies and its applications in forests.