Rapid foliar uptake of inorganic and amino acid nitrogen in three dryland plant species

Abstract

Background and aims Dryland primary production is often nitrogen (N) limited due in part to spatiotemporal decoupling of soil nutrient availability and plant uptake. Our aim is to quantify inorganic and organic N uptake at daily timescales to compare short-term nutrient acquisition patterns among dryland plant species. Methods We assessed N uptake in three commonly co-occurring perennial plant species from a Chihuahuan Desert grassland (a C₄ grass, C₃ grass, and C₃ subshrub). In the greenhouse, we applied ¹⁵N-ammonium, nitrate, or glutamate tracers to plant roots and quantified uptake and recovery in leaves after 12, 24, and 48 h. Results Plants took up inorganic and amino acid N to leaves as rapidly as 12 h following application, and uptake more than doubled between 24 and 48 h. Inorganic N uptake was 3-4x higher than glutamate in all three species, and plants took up ammonium and nitrate at 2-3x faster rates overall. On average, Bouteloua eriopoda had the highest inorganic N recovery and uptake rates, while Gutierrezia sarothrae had the highest glutamate uptake over time. Achnatherum hymenoides uptake was ~ 50% lower than the other two species after 48 h. Conclusion Plants showed similar patterns of short-term foliar uptake and recovery indicating a lack of niche partitioning by N form among the three dryland species measured. Our results suggest that soil inorganic N, particularly nitrate, may comprise a greater proportion of plant N nutrition than amino acid-N and may be more widely exploited following a precipitation pulse in this habitat.