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

供给0～0.6 mg N的盆栽荫香(Cinnamomum burmannii)幼树分别生长在倍增CO ₂(+CO₂，731 μmol·mol^-1)和正常空气CO ₂浓度(CO ₂，365 μmol·mol^-1)的生长箱内，昼夜温度分别为25/23 ℃和32/25 ℃，自然光照下生长30 d.以生长在CO₂和25/23 ℃下的植株为对照研究增温和氮对+CO₂叶片光合作用的影响.结果表明，在+CO₂和25/23 ℃下无氮和氮处理植株的平均光合速率(Pnsat)较+CO₂和32/25 ℃下的叶片高5.1%，温度增高降低叶片Pnsat；而Pnsat随供氮而增高.在+CO₂条件下，生长在32/25 ℃下的叶片Rubisco最大羧化速率(Vcmax)和最大电子传递速率(Jmax)较25/23 ℃下的低(P＜0.05)，温度增高降低+CO₂下叶片的Vcmax和Jmax在+CO2下叶片光合呼吸速率(Rp)较低，生长温度增高提升Rp.在CO₂下生长温度从25/23 ℃增至32/25 ℃，叶片的Rubisco含量(NR)和Rubisco活化中心浓度(M)降低，而供氮能增高NR和M.供氮能减缓温度增高对倍增CO₂下荫香叶片光合作用的限制.

Effects of nitrate application on alleviating photosynthesis restriction of Cinnamomum burmannii leaves under elevated CO2 concentration and enhanced temperature

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.