Effects of nitrogen deposition and UV-B radiation on seedling performance of Chinese tallow tree (Triadica sebifera): A photosynthesis perspective

Abstract

Chinese tallow tree (Triadica sebifera) is native to China but is aggressively invading plant species in southeastern USA Growth of invasive T. sebifera has been shown to be promoted by N deposition and inhibited by UV-B radiation, and outperform that of the native origin, which indicate higher photosynthesis ability of the invasive origin. In T. sebifera’s native range, soil sterilization could increase its performance by suppression of soil pathogens. However, the interactive effects among these factors on photosynthetic characteristics of both native and invasive T. sebifera are still not understood. Here, we conducted a pot-experiment with both native and invasive populations of T. sebifera to test how N deposition, UV-B radiation and soil sterilization affect T. sebifera performance with respect to biomass and photosynthetic ability. Total biomass and the effective quantum yield of photosystem II (Y(II), correlates to plant CO2 assimilation) of invasive populations were higher, but the maximum quantum yield of photosystem II (Fv/Fm, a stress indicator) was lower than that of the native populations in sterilized soil. Leaf biomass and leaf area of invasive populations were higher than that of the native populations. Leaf area of both native and invasive populations, total biomass of native populations and relative chlorophyll content of invasive populations were increased by N deposition. Leaf area of invasive populations was increased but that of the native populations was not affected by N deposition in sterilized soil. Y(II) was reduced by UV-B radiation and soil sterilization. These results suggest invasive T. sebifera populations were higher in CO2 assimilation rate and lower in resistance to environmental stress. The stronger performance of T. sebifera from the invasive range could have been facilitated by N deposition via increased leaf area in sterilized soil even though no significant differences were observed by N deposition in active soil. The photosynthesis response of invasive plants to current global change factors should be considered in future studies determining differences in plant performance between the native and the invasive range and efficient management of invasive species.