Influence of nitrogen and phosphorus additions on parameters of photosynthesis and chlorophyll fluorescence in Cyclocarya paliurus seedlings.

Abstract

Cyclocarya paliurus has been traditionally used as a functional food in China. A hydroponic experiment was conducted to determine the effects of N and P additions on photosynthesis and chlorophyll fluorescence (ChlF) of C. paliurus seedlings. N and P additions significantly altered photosynthesis and ChlF in the seedlings, but responses of these parameters to the N and P concentrations varied at different developmental stages. The greatest net photosynthetic rate (P _N) and actual photochemical efficiency of PSII (Ф_PSII) occurred in the treatment of 150.0 mg(N) L^-1 and 25.0 mg(P) L^-1 addition, whereas the highest maximum quantum yield of PSII (F_v/F_m) and water-use efficiency (WUE) were recorded with 150.0 mg(N) L^-1 and 15.0 mg(P) L^-1 on the 60^th day after treatment. Significantly positive correlations of P _N with leaf relative chlorophyll content, transpiration rate, WUE, F_v/F_m, and Φ_PSII, as well as the Ф_PSII with the F_v/F_m, were found. Our results indicated that an optimal addition of N and P nutrients depends on their coupling effects on the photosynthetic capacity and PSII photochemistry.