Effects of nitrogen and phosphorus fertilization on leaf carbon, nitrogen and phosphorus stoichiometry of Arabidopsis thaliana

Abstract

Aims Arabidopsis thaliana, a widely used model organism in plant biology, is an ideal plant to test the growth rate hypothesis (GRH) and homeostasis theory about plant nutrition. Our objectives are to test i) whether GRH applies to this plant species, ii) how leaf nitrogen (N) and phosphorus (P) of A. thaliana follow the homeostasis theory and iii) whether the allometric relationship between leaf N and P content is consistent with the 3/4 power function (N-P 3/4 ) for individual plant species. Methods Based on a pot experiment in a phytotron with N and P fertilizer additions, we measured the leaf car- bon (C), N and P content and leaf biomass of A. thaliana. Specific growth rate (mg·mg -1 ·d -1 ) was the leaf biomass increment divided by the initial biomass at planting, and by the days after planting. The homeostasis of plant ele- ments is indicated by the exponent (reciprocal of the regulation coefficient) of the power function of leaf nutrient against soil nutrient concentrations. Important findings P is the limiting nutrient of the culture substrate for A. thaliana, while N fertilization could cause toxic effects in cases of excessive N uptake. The growth of A. thaliana is consistent with GRH—the specific growth rate decreases with increasing leaf N:P or C:P. Leaf P content shows a significant regulation coefficient (3.51) (leaf-P-substrate-P 1/3.51 ), but leaf N content has no significant relationship with substrate N. There is a sig- nificant allometric relationship between leaf N and P content, which is inconsistent with the 3/4 power function (N-P 3/4 ). The power exponent (0.209) between leaf N content and leaf P content in the P fertilization treatments is significantly lower than the exponent (0.466) in the N fertilization treatments, suggesting that fertilization may affect the allometry between nutrients. Our findings can offer reference for future field studies on plant ecological stoichiometry at scales from species to community to ecosystem.