Evaluation of methods to measure differential 15N labeling of soil and root N pools for studies of root exudation
Evaluation of methods to measure differential 15N labeling of soil and root N pools for studies of root exudation
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DOI：
10.1002/rcm.1615
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发表时间：
2004-01-01
影响因子：
2
通讯作者：
Wanek, W
中科院分区：
文献类型：
--
作者：
Hertenberger, G;Wanek, W
为研究油菜、矢车菊和多年生黑麦草根系分泌物的分布规律，采用硝酸铵原位标记技术，研究了不同标记方法的有效性。茎渗透被发现有效地标记植物与较厚的茎，而对于草种，切割和浸泡到N-15溶液的叶尖被证明是最有效的。微扩散技术分离铵，结合常规的阳离子交换色谱分离硝酸盐的氨基-N化合物，此后，被发现适合分离的N馏分的植物和土壤提取物N-15测定。然后在营养液中培养所有三个物种，并通过茎补料用（NH 4 NO3）-N-15-N-15标记42小时。大量的根和芽以及热水提取物的N-15标记的动力学进行了评估，并高达1.1%的N-15过量（APE）被发现在营养液中。L.多年生植物的氨基酸组成为甘氨酸、丝氨酸、丙氨酸和天冬氨酸。为了评估这套方法在田间环境中研究根系分泌物的适用性，L。在含有低营养土壤的盆中不添加肥料地种植多年生植物。植物N-15标记通过尖端浸泡和N-15和N浓度进行了分析，在芽，根和土壤中，在48小时的间隔。地上部达到1.25 APE，根和土壤分别为0.10和0.005 APE。4%（48小时）和6%（24小时）的植物N-15的总渗出到土壤中。在根中，氨基酸组成的可溶性N-15库的比例最大，而土壤N-15水平相似的氨基酸和铵，超过硝酸盐。简要讨论了氮组分从根系向土壤转移的机制。版权所有（C）2004约翰威利父子有限公司。
To study patterns of root exudation, the effectiveness of different techniques for in situ N-15 labeling of Brassica napus, Centaurea jacea and Lolium perenne with ammonium nitrate was tested. Stem infiltration was found to effectively label plants with thicker stems, whereas, for grass species, cutting and immersing the leaf tips into N-15 solution proved to be most effective. A microdiffusion technique to isolate ammonium, combined with conventional cation-exchange chromatography to separate nitrate from amino-N compounds thereafter, was found suitable for separation of the N fractions of plant and soil extracts for N-15 determination. All three species were then cultivated in nutrient solution and labeled with (NH4NO3)-N-15-N-15 by stem feeding for 42 hours. Kinetics of N-15 labeling of bulk roots and shoots as well as hot water extractable material were assessed, and up to 1.1 at% N-15 excess (APE) was found in nutrient solutions. The main amino acids exuded by L. perenne were glycine, serine, alanine and aspartic acid. To assess the suitability of this set of methods to study root exudation in field settings, L. perenne was grown without fertiliser addition in pots containing low-nutrient soil. Plants were N-15 labeled via tip immersion and N-15 and N concentrations were analysed in shoots, roots and soils during a 48-h interval. Shoots reached 1.25 APE, roots and soil 0.10 and 0.005 APE, respectively. Between 4% (48 h) and 6% (24 h) of total plant N-15 was exuded by roots into the soil. In roots amino acids comprised the largest proportion of the soluble N-15 pool, whereas Soil N-15 levels were similar for amino acids and ammonium, exceeding those of nitrate. Mechanisms for the shift within N fractions from roots to soils are briefly discussed. Copyright (C) 2004 John Wiley Sons, Ltd.