Effects of nitrate application on alleviating photosynthesis restriction of Cinnamomum burmannii leaves under elevated CO2 concentration and enhanced temperature
供氮和增温对倍增二氧化碳浓度下荫香叶片光合作用的影响

In this study, potted C. burmannii saplings were cultured in a top-closed chamber with elevated CO2 (+ CO2, 731 micromol x mol(-1)) and ambient CO2(CO2, 365 micromol x mol(-1)), and at diurnal temperature (day/night) 25/23 degrees C and 32/25 degrees C, respectively. The gas exchange, calculated photosynthesis parameter, Rubisco content, and activated state of Rubisco were examined. The results showed that under + CO2 and at 25/23 degrees C, the mean photosynthetic rate (Pnsat) of sapling leaves was 5.1% higher than that under + CO2 and at 32/25 degrees C. Temperature enhancement declined Pnsat, while nitrate addition increased it. Under + CO2, saplings had lower V(cmax) and J(max) at 32/25 degrees C than at 25/23 degrees C. Temperature enhancement under + CO2 also declined V(cmax) and J(max). Under + CO2, lower photorespiration rate (Rp) occurred in leaves, but temperature enhancement could increase Rp. Under + CO2, Rubisco content (NR) and its active site per unit leaf area (M) decreased as diurnal temperature changed from 25/23 degrees C to 32/25 degrees C. Meanwhile, nitrate addition could increase NR and M. It may be suggested that nitrate addition could alleviate the restriction of photosynthesis under elevated CO2 concentration and enhanced temperature.