Photosynthesis of Hosta under Light and Controlled-Release Nitrogen Fertilizer

The interactive effects of light intensity and controlled-release nitrogen fertilizer (CRNF) supply on growth, gas exchange, and chlorophyll (Chl) fluorescence parameters of two species of potted Hosta seedlings, original species of the genus Hosta in China, were studied. N-4 (4 g of CRNF per pot), N-8 (8 g of CRNF per pot), and sometimes N-12 (12 g of CRNF per pot), significantly increased total dry weights, net photosynthetic rate (P-N), stomatal conductance (g(s)), transpiration rate (E), the maximum quantum yield of PSII photochemistry (F-v/F-m), the maximum ratio of quantum yields of photochemical and concurrent nonphotochemical processes in PSII (F-v/F-0), actual efficiency of photochemical energy conversion in PSII under light (Phi(PSII)), and photochemical quenching coefficient (qP), but significantly decreased internal CO2 concentration (C-i) and nonphotochemical Chl fluorescence quenching (NPQ) compared to control plants at different growth stages of the two Hosta species in two levels of light intensities (50% of natural light (L-50) and 70% of natural light (L-70)). Based on the available data, we concluded that the increments in total dry weights of Hosta clausa var. ensata and Hosta ventricosa by appropriate amount of CRNF supply treatments under L-50 and/or L-70 light conditions are directly related to the increments in the P-N, which may be due to both stomatal and nonstomatal improvements for a longer growing time. Furthermore, there was an interaction between light intensity and CRNF supply treatments on growth and photosynthetic characteristics of the two Hosta species. The adaptability of Hosta plants with obvious stoloniferous rootstock to stronger light was higher than that of Hosta plants without obvious stoloniferous rootstock.