Foliar Fertilization of Dual-Labeled Organic and Inorganic N in Rice; Mechanisms of Transport and Assimilation

The absorption, transport, and assimilation mechanism of organic and inorganic nitrogen(N) in rice organs were analyzed by applying 13C-15N dual-labeled organic and inorganic N directly to the leaves of rice plants (variety: C Liangyou 266) at tillering stage based on isotope tracing. The findings suggest that the dry weight and N accumulation of various rice organs under glycine N and ammonium N treatments were significantly higher than other treatments; the dry weight and N accumulation in rice organs followed the pattern of “leaf > root > stem”, and there were no significant differences between control and nitrate N treatment. The 15N increments were detected in the roots, stems and leaves of all treatments, showing a certain pattern of “leaf > stem > root”; there were significant differences between the 15N increments of various organs (P < 0.01). The 13C increment/15N increment ratios of rice root, stem, leaf, and whole plant were 0.108, 0.158, 0.178, and 0.161 respectively. For rice plants treated by glycine N and ammonium N, the activity of GOT, GPT and GDH peaked in leaves, followed by stems and then roots; while the pattern of activity for GOT, GPT and GDH in the control (Ck) and nitrate N group was in following order “leaf > root > stem”. The results showed that rice leaves directly absorb and utilize molecular glycine and the absorption rate of glycine is significantly higher than ammonium N or nitrate N. Molecular organic N absorbed into rice leaves would be transported to roots; the transportability of N in rice plants ranked in descending order is as follows: amino acid N > ammonium N > nitrate N. © 2022 Friends Science Publishers