Work

Nitrogen Isotope Fractionation During Nitrate and Ammonium Uptake in Maize: Hydroponic Evidence and Implications for Ecological Investigations

Year: 2025

Type: article

Abstract: ABSTRACT Understanding nitrogen (N) isotopic fractionation during plant uptake is critical for interpreting δ 15 N variations in terrestrial ecosystems. We investigated isotopic discrimination during ammonium (NH 4 + ) or nitrate (NO 3 − ) uptake in maize (Zea mays) grown hydroponically under controlled conditions with 0.2 and 2 mM to represent high and low affinity transport systems, respectively. Nitrogen ( 15 ε) and oxygen ( 18 ε) isotopic fractionation during NO 3 − uptake were determined. NO 3 − uptake exhibited low and concentration‐independent 15 ε values (0.2 mM: 15 ε = −2‰; 2 mM: 15 ε = −1.7‰). In contrast, 18 ε was lower at high concentrations (0.2 mM: 18 ε = −5.3‰; 2 mM: 18 ε = −2.1‰). For NH 4 + uptake, 15 ε was higher and increased with concentration (0.2 mM: 15 ε = −5.7‰; 2 mM: 15 ε = −8.5‰). An isotope mixing model suggests a small NO 3 − efflux contributes to 15 N and 18 O enrichment in solution due to significant isotopic fractionation during assimilation. The discrimination between source and plant δ 15 N is influenced by the source δ 15 N, the magnitude of 15 ε, N supply, and uptake kinetics. While plant δ 15 N integrates source δ 15 N over time, it is unsuitable as a direct tracer. This study refines the understanding of isotopic fractionation mechanisms in plant N uptake and their implications for δ 15 N‐based ecological investigations.

Source: Plant Cell & Environment

DOI: 10.1111/pce.70330

Authors: Priscillia Semaoune, Joëlle Templier, Sylvie Derenne, R. Dave Evans, Mathieu Sebilo

Institutions: Sorbonne Université, Washington State University

Language: English

Topic: Isotope Analysis in Ecology

Subfield: Ecology

Field: Environmental Science

Domain: Physical Sciences

SDG: Zero hunger

Open Access status: hybrid

Estimated APC paid: $5,440