Nutrient addition affects leaf N-P scaling relationship in Arabidopsis thaliana

Ambient nutrient changes influence the coupling of nitrogen (N) and phosphorus (P) in terrestrial ecosystems, but whether it could alter the scaling relationship of plant leaf N to P concentrations remains unclear. Moreover, knowledge about how multi-elemental stoichiometry responds to varying N and P availabilities remains limited. Here we conducted experimental manipulations using Arabidopsis thaliana, with five N and P addition levels and nine repeated experiments. We found that the scaling exponent of leaf N to P concentrations decreased with increasing N levels, but increased with increasing P levels. This suggests that high nutrient availability decreases the variability of its own concentration, but promotes the fluctuation in another tightly associated nutrient concentration in leaves among plant individuals. We call this as Nutrient Availability–Individual Variability Hypothesis. In addition, N and P supply exerted differential influences on the concentrations of multi-elements in leaves. Compared with the green-leaves, the senesced-leaves had higher variability of C, N, P, K and Mg concentrations but lower variability of Ca concentration under varying nutrient availabilities. This suggests that stage-dependent pattern of leaf stoichiometric homeostasis relies on the type of elements, and the elemental feature should be considered when choosing a more favorable tissue in plants for diagnosing the nutrient availability in ambient environments. These findings provide a novel mechanism for understanding the dynamic processes of population structure and functioning under global nutrient changes, which should be incorporated into modeling stoichiometric growth in terrestrial ecosystems. Furthermore, our study can advance the holistic understanding about plant eco-physiological response and adaption under global nutrient changes from the stoichiometric perspective of multiple elements beyond N and P.