Abstract: The content and stoichiometry of nutrients in plant tissue reflect the distribution and interaction of elements in plants, as well as plant nutrient use efficiency and the nutrient limitation of the environment. Here, we analyzed the effects of four light intensities (full light, 50%, 75% and 95% shading) on the growth and the contents and stoichiometric characteristics of C, N, P, and K in Firmianaplatanifolia seedlings. Results showed that shading significantly affected growth traits, biomass, element content and accumulation, and stoichiometric ratio of seedlings (P<0.05). The height and specific leaf area of seedlings increased with the increases of shading intensity, while the basal diameter and roughness decreased. The total biomass was the highest under 75% shade and the lowest under 95% shade. Across those shading treatments, foliar C, N, P and K concentrations were higher than that in roots and stems. The N content in different organs followed the order of leaf>root>stem, while K content was in order of leaf>stem>root. The total accumulation of C, P and K increased with the increases of shading intensity, with the maximum and minimum values occurring under 75% shade and 95% shade, respectively. The changes of C∶N and C∶P of seedlings were similar, which increased first and then decreased with the increases of shading intensity, and reached the maximum value under 50% shading. N∶P in each organ was much lower than 14, indicating that seedling growth under different shading conditions was severely restricted by nitrogen availability. Our results highlight that shading can regulate the nutrient accumulation and distribution of F.platanifolia seedlings under different light environments, with consequences on biomass production. The 75% shading is optimal for seedling breeding, which helps to increase the height, specific leaf area, biomass, nutrient content and accumulation. Excessive shading might inhibit seedling growth.

Key words: shading, biomass, element content, accumulation, stoichiometric ratio.