Simple method to enable the high resolution determination of total free amino acids in soil solutions and soil extracts
Simple method to enable the high resolution determination of total free amino acids in soil solutions and soil extracts
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DOI：
10.1016/s0038-0717(02)00203-1
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发表时间：
2002-12-01
影响因子：
9.7
通讯作者：
Farrar, JF
中科院分区：
文献类型：
--
作者：
Jones, DL;Owen, AG;Farrar, JF
无论是游离态还是聚合态的氨基酸，对大多数生态系统来说都是氮素的重要补充，因此构成了土壤氮素循环中的一个关键库。一些植物直接从土壤中吸收氨基酸的能力可能会带来竞争优势，特别是在氮素有限的环境中。虽然无机氮浓度(NH4+和NO3-)的测量通常是在土壤溶液或土壤水/KCl萃取物上进行的，但需要一个补充程序来确定游离氨基酸，并能够确定所有植物可用的库。本研究的目的是建立和测试一种快速、灵敏地测定土壤溶液和土壤浸出物(水或2M KCl2)中总游离氨基酸的方法，并将其与Moore和Stein(1954)的标准三酮法进行比较。荧光分光光度法依赖于游离氨基酸与邻苯二甲醛和β-硫醇的反应。这种荧光分光光度法比一般的吲哚试剂分光光度法(工作范围10-500微米)要灵敏得多(工作范围为0.1-50微米)。此外，该方法只需要很小的样品体积(0.1-50微米)，快速(1分钟样品(-1))，操作简单，在三个数量级的浓度范围(0.1-100微米)内呈线性。该方法被用来测定一系列生态系统类型(高地和低地草原、森林、荒地和沿海盐沼)的游离氨基酸浓度。一般来说，土壤溶液中游离氨基酸的浓度较低，且相对独立于土壤类型。所有站点(n=7)的平均可溶性氮浓度分别为：氨基酸24+/-8um，NH4+39+/-14um，NO3-67+/-42um。游离氨基酸通常占土壤溶液中总可溶性氮的10-40%，因此构成了土壤中大量的可溶性氮和植物有效态氮。(C)2002爱思唯尔科学有限公司。保留所有权利。
Amino acids, either in a free or polymeric state, represent a significant addition of N to most ecosystems and therefore comprise a key pool in the soil nitrogen cycle. The ability of some plants to take up amino acids directly from soil may confer a competitive advantage particularly in N-limited environments. Whilst measurements of inorganic N concentrations (NH4+ and NO3-) are routinely undertaken on either soil solutions or soil water/KCl extracts, there is a need,for a supplementary procedure to determine free amino acids and enable determination of all plant-available pools. The aim of this study is to develop and test a procedure for the rapid and sensitive determination of total free amino acids in soil solutions and soil extracts (water or 2 M KCl) and to compare this with the standard ninhydrin method of Moore and Stein (1954). The spectrofluorometric procedure relies on the reaction of free amino acids with o-phthaldialdehyde and beta-mercaptoethanol. The fluorometric method is much more sensitive (working range 0.1-50 muM) than typical spectrophotometric analysis procedures for free amino acids which employs the ninhydrin reagent (working range 10-500 muM). In addition, the method only requires small sample volumes (0.1-50 mul), is rapid (1 min sample(-1)), simple to perform, and linear over a concentration range of three orders of magnitude (0.1-100 muM). The method was used to determine free amino acid concentrations across a range of ecosystem types (upland and lowland grasslands, forest, heathland and coastal saltmarsh). Generally, the concentration of free amino acids in soil solution was low and relatively independent of soil type. The average soluble N concentrations across all sites (n = 7) were 24 +/- 8 muM for amino acids, 39 +/- 14 muM for NH4+ and 67 +/- 42 muM for NO3-. Free amino acids typically constituted 10-40% of the total soluble N in the soil solution and therefore comprise a significant soluble N and plant available pool in soil. (C) 2002 Elsevier Science Ltd. All rights reserved.