Application of Nitrate, Ammonium, or Urea Changes the Concentrations of Ureides, Urea, Amino Acids and Other Metabolites in Xylem Sap and in the Organs of Soybean Plants (Glycine max (L.) Merr.)

Abstract

Soybean (Glycine max (L.) Merr.) plants form root nodules and fix atmospheric dinitrogen, while also utilizing the combined nitrogen absorbed from roots. In this study, nodulated soybean plants were supplied with 5 mM N nitrate, ammonium, or urea for 3 days, and the changes in metabolite concentrations in the xylem sap and each organ were analyzed. The ureide concentration in the xylem sap was the highest in the control plants that were supplied with an N-free nutrient solution, but nitrate and asparagine were the principal compounds in the xylem sap with nitrate treatment. The metabolite concentrations in both the xylem sap and each organ were similar between the ammonium and urea treatments. Considerable amounts of urea were present in the xylem sap and all the organs among all the treatments. Positive correlations were observed between the ureides and urea concentrations in the xylem sap as well as in the roots and leaves, although no correlations were observed between the urea and arginine concentrations, suggesting that urea may have originated from ureide degradation in soybean plants, possibly in the roots. This is the first finding of the possibility of ureide degradation to urea in the underground organs of soybean plants.

Effects of Nodulation on Metabolite Concentrations in Xylem Sap and in the Organs of Soybean Plants Supplied with Different N Forms

“…In the NO 3 − treatment for 1 day, the concentrations of allantoin and allantoate significantly decreased compared with the Cont xylem sap. Ono et al [ 15 ] reported that 3 days of 5 mM NO 3 − treatment decreased the ureides concentration in the xylem by approximately one-seventh of the control plants. The NH 4 + treatment increased the concentrations of Asn and Gln but did not affect the allantoate and allantoin concentrations ( Figure 2 A).…”

“…A high concentration of ammonium may be related to the promotion of ureide synthesis [ 13 ]. It was suggested that N fixed in the nodules and N absorbed from the roots were differentially transported to the shoots [ 14 , 15 ]. The absorbed N, especially NO 3 − is initially transported to the leave and assimilated there, and the N is redistributed to the pods and seeds.…”

Efecto del N mineral y N2 sobre la nutrición nitrogenada en la planta de soya

“…Importante es señalar que entre las etapas de R2 y R4, las plantas abastecidas con 3.5 meq de N presentaron 79% del N soluble transportado como N ureido, observándose que dicha forma de N se redujo a 50% cuando la planta recibió 7 meq de N en la solución nutritiva. Las disminuciones en la cantidad de N-ureido por efecto de la aplicación externa de N habían sido reportadas por Ono et al (2021), dichos investigadores mencionaron que en plantas noduladas el N-ureido resulta relativamente bajo, debido a que se convierte a urea, ocurriendo activamente en las partes subterráneas, especialmente en las raíces, en su estudio, el nitrato represento alrededor de 50% de N aplicando 5 mM de NaNO3.…”

“…Estos resultados indican que en las plantas de soya noduladas la acumulación de MS en las vainas es favorecidas por la actividad de los nódulos y que el follaje es una fuente importante de N, pudiendo concluir que el N fijado (N-ureido) es destinado prioritariamente al abastecimiento de granos como lo mencionaron (Anglade et al, 2015;Zhou et al, 2016;Ono et al, 2021).…”

Integrated Proteomics and Metabolomics Analysis of Nitrogen System Regulation on Soybean Plant Nodulation and Nitrogen Fixation

“…However, exposing soybean roots to high concentrations of nitrogen can inhibit root nodule growth, accelerate root nodule senescence, and reduce the efficiency of nitrogen fixation [ 1 , 2 ]. The effects of exogenous nitrogen on nodulation and nitrogen fixation in soybeans are influenced by nitrogen concentration, application site, and treatment time, among other factors [ 3 , 4 , 5 , 6 , 7 , 8 ]. Exogenous nitrogen was separately supplied to the upper and lower layers of soybean roots [ 9 , 10 ] or supplied to the left and right sides of dual-root soybeans [ 11 , 12 ], and all showed a rapid and reversible effect of nitrogen on root nodule growth and nitrogenase activity.…”