Effects of light intensity and nitrogen deposition on ecophysiological characteristics of Coreopsis grandiflora1

Abstract

Light heterogeneity commonly occurs in natural environments, and N deposition has increased sharply in recent decades, affecting both the growth and invasion of exotic plants. We used an exotic species, Coreopsis grandiflora, distributed in natural and urban areas throughout China, to study the combined effects of light exposure and N addition on leaf physiology, height, crown area, total biomass (TB), and phenotypic plasticity. We exposed C. grandiflora seedlings to one of three light (15, 65, and 100% of full irradiation) and one of three nitrogen treatments (0, 8, and 20 g N m–2 yr–1). The shade significantly increased leaf chlorophyll, N, and P concentrations, aboveground biomass allocation, and specific leaf area, allowing plants to capture more light, which did not result in a change in TB, indicating that C. grandiflora seedlings have shade tolerance. Nitrogen addition generally increased the TB, leaf biomass, crown area and leaf N concentration. In addition, N supply did not increase TB of C. grandiflora in the shade. For approximately half of the traits measured, the phenotypic plasticities of C. grandiflora responding to light differ greatly from those responding to N addition. Under light and N deposition treatments, photosynthetic N use efficiency had higher phenotypic plasticity than other leaf physiological traits, whereas the maximum quantum yield of photosystem II, leaf N, and P concentrations had lower phenotypic plasticity, suggesting that hierarchical plasticity occurs among the various leaf physiological traits. Light intensity increased the plasticity of C. grandiflora in response to N deposition. Thus, with high plasticity, invasiveness of C. grandiflora may increase under high N deposition and illumination conditions.