Plant organic nitrogen nutrition: costs, benefits, and carbon use efficiency

Tünnermann, L., Aguetoni Cambui, C., Franklin, O. ORCID: https://orcid.org/0000-0002-0376-4140, Merkel, P., Näsholm, T., & Gratz, R. (2024). Plant organic nitrogen nutrition: costs, benefits, and carbon use efficiency. New Phytologist 10.1111/nph.20285. (In Press)

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Abstract

Differences in soil mobility and assimilation costs between organic and inorganic nitrogen (N) compounds would hypothetically induce plant phenotypic plasticity to optimize acquisition of, and performance on, the different N forms. Here we evaluated this hypothesis experimentally and theoretically. We grew Arabidopsis in split-root setups combined with stable isotope labelling to study uptake and distribution of carbon (C) and N from l-glutamine (l-gln) and NO3 - and assessed the effect of the N source on biomass partitioning and carbon use efficiency (CUE). Analyses of stable isotopes showed that 40-48% of C acquired from l-gln resided in plants, contributing 7-8% to total C of both shoots and roots. Plants grown on l-gln exhibited increased root mass fraction and root hair length and a significantly lower N uptake rate per unit root biomass but displayed significantly enhanced CUE. Our data suggests that organic N nutrition is linked to a particular phenotype with extensive growth of roots and root hairs that optimizes for uptake of less mobile N forms. Increased CUE and lower N uptake per unit root growth may be key facets linked to the organic N phenotype.

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