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.