The free amino acids play an important role in total nitrogen (N) absorption for plants. Most previous studies, however, only focused on the organic N uptake of glycine or several simple amino acids by plants. The purpose of this research was to quantify the uptake rate of N derived from multiple amino acids and evaluate the importance of different N forms (amino acid N and inorganic N) to plant nutrition. A range of amino acids (aspartic acid, lysine, leucine, phenylalanine, proline, valine, alanine, glutamine, isoleucine and glycine) and inorganic N (NH₄⁺ and NO₃^-) with the same amount of N for each of 12 N forms were used in a short-term (3 h) ¹⁵N labeling experiment in a temperate grassland of North China. Two dominant plant species, Stipa grandis and L. chinensis, were investigated. Within 3 h, the N derived from multiple amino acids were both absorbed by S. grandis and L. chinensis, contributed about 25% and 37% to the total N uptake by two plant species, respectively. Leymus chinensis is relatively more effective in utilizing N derived from amino acids compared to S. grandis, while S. grandis takes up more inorganic N of NH₄⁺ and NO₃^-. The uptake rates of N derived from multiple amino acids by S. grandis and L. chinensis differed greatly, and which have significant positive relations with soil amino acid concentrations (r² = 0.59, P < 0.05; r² = 0.81, P < 0.001). The largest uptake rate of N derived from multiple amino acids by S. grandis and L. chinensis was aspartic acid and glycine, respectively. Our findings confirm that the N derived from amino acids may be an important N source for plant growth in the temperate grasslands of North China. In order to unveil the N utilization in the grasslands ecosystem, in the future, more forms of the dual labeled (¹³C,¹⁵N) amino acids and other organic N should be used in the in situ field experiment.

游离氨基酸在植物吸收总氮（N）中起重要作用。但是，大多数以前的研究仅关注植物对甘氨酸或几种简单氨基酸的有机氮吸收。这项研究的目的是量化源自多种氨基酸的N的吸收率，并评估不同N形式（氨基酸N和无机N）对植物营养的重要性。一系列氨基酸（天冬氨酸，赖氨酸，亮氨酸，苯丙氨酸，脯氨酸，缬氨酸，丙氨酸，谷氨酰胺，异亮氨酸和甘氨酸）和无机氮（NH ₄ ⁺和NO ₃ ^-为每个的12 N相同数量的N）短期（3小时）使用表格¹⁵在华北温带草原进行N标记实验。调查了两个主要的植物物种，大针茅和中华绒螯蟹。在3 h内，源自多种氨基酸的N均被S. grandis和L. chinensis吸收，分别占两种植物吸收N总量的25％和37％。羊草是在利用n的相比氨基酸衍生相对更有效的针茅，而针茅占用NH的更无机氮₄ ⁺和NO ₃ ^- 。N的吸收速率从多个氨基酸衍生通过针茅中华绒螯蟹和中华绒螯蟹之间的差异很大，并且与土壤氨基酸浓度呈显着正相关（r ²  = 0.59，P  <0.05； r ²  = 0.81，P  <0.001）。S. grandis和L. chinensis从多种氨基酸中吸收的最大N分别是天冬氨酸和甘氨酸。我们的发现证实，氨基酸的氮可能是华北温带草原植物生长的重要氮源。为了揭示草地生态系统中的氮利用情况，将来，会有更多形式的双标记（¹³ C，¹⁵N）氨基酸和其他有机氮应在现场实验中使用。