AMINO-ACID-COMPOSITION IN XYLEM SAP OF SOYBEAN RELATED TO THE EVALUATION OF N-2 FIXATION BY THE RELATIVE UREIDE METHOD
AMINO-ACID-COMPOSITION IN XYLEM SAP OF SOYBEAN RELATED TO THE EVALUATION OF N-2 FIXATION BY THE RELATIVE UREIDE METHOD
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DOI：
10.1080/00380768.1995.10419562
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发表时间：
1995-03-01
影响因子：
2
通讯作者：
OHYAMA, T
中科院分区：
文献类型：
--
作者：
OHTAKE, N;NISHIWAKI, T;OHYAMA, T
为了通过相对酰脲法估算大豆（Glycine max (L.) Merr.）的N-2固定量，我们修改了Herridge等人提出的原始方程[酰脲-N/(酰脲-N + α-氨基-N + 硝酸盐-N)]。为[脲化物-N/(脲化物N+2Xα-氨基-N+硝酸盐-N)]，基于观察到一个分子中具有两个N原子的天冬酰胺是大豆植物木质部汁液中的主要氨基酸。然而，由于氨基酸组成可能会随着生长阶段或氮利用率等环境因素而变化，因此有必要确定“2X”因子是否合适。本文对大豆品种木质部汁液中氨基酸和酰胺的含量及相对组成进行了分析。大田种植的恩瑞，经过3种肥料处理，即底施少量硫酸铵、深施或追施包膜尿素（缓释氮肥）。虽然氨基酸和酰胺的组成随施肥处理或生长阶段的不同而变化，但主要形式始终是天冬酰胺。天冬酰胺以及谷氨酰胺、精氨酸和组氨酸的浓度随着生长直至R5阶段而增加。缬氨酸、赖氨酸、苏氨酸、异亮氨酸、亮氨酸、苯丙氨酸和丝氨酸的水平在成熟阶段显着升高。相比之下，谷氨酸、GABA、丙氨酸和甘氨酸的水平随着成熟而下降。对照处理中，直至R3期，天冬酰胺的比例约占总氨基-N的30-40%，成熟时则增加至50%左右。无论是深施还是追施包膜尿素，R5阶段天冬酰胺的比例均超过70%。无论施肥处理或生育阶段，氨基酸分析仪测定，每个氨基化合物的平均氮原子数相对恒定，为1.5至1.9（平均1.7）。总之，证实基于 2X α-氨基-N 方程的相对脲化物-N 值比原始方程更相关，与阶段和肥料处理无关。
For the estimation of N-2 fixation of soybean (Glycine max (L.) Merr.) by the relative ureide method, we modified the original equation [ureide-N/(ureide-N + alpha-amino- N + nitrate-N)] proposed by Herridge et al. to [ureide-N/(ureide N + 2X alpha-amino-N+nitrate-N)], based on the observation that asparagine which has two N atoms in one molecule was the major amino acid in the xylem sap of soybean plants. However, since the amino acid composition may change with the growth stages or environmental factors such as N availability, it is necessary to determine whether the factor ''2X'' is appropriate. In the present paper, the experiments were carried out to analyze the levels and relative composition of amino acids and amides in the xylem sap of soybean cv. Enrei which was grown in the field with three fertilizer treatments, i.e. control with a small amount of basal dressing of ammonium sulfate, deep placement or top dressing of coated urea (slow release N fertilizer).Although the composition of the amino acids and amides changed with the fertilizer treatments or growth stages, the major form was always asparagine. The concentration of asparagine as well as glutamine, arginine, and histidine increased with growth till the R5 stage. The levels of valine, lysine, threonine, isoleucine, leucine, phenylalanine, and serine rose remarkably at the maturation stage. In contrast, the levels of glutamic acid, GABA, alanine, and glycine decreased through maturation. In the control treatment, the proportion of asparagine accounted for about 30-40% of total amino-N till the R3 stage, then increased to about 50% at maturation. The proportion of asparagine exceeded 70% at the R5 stage with either deep placement or top dressing of coated urea.Irrespective of fertilizer treatments or growth stages, the average number of N atoms per amino compound was relatively constant, ranging from 1.5 to 1.9 (average 1.7) based on determinations by the amino acid analyzer. In conclusion, it was confirmed that the relative ureide-N values based on the 2X alpha-amino-N equation are more relevant irrespective of stages and fertilizer treatments than the original equation.