A local popular Japonica rice (Oryza sating L.) cultivar, Nanjing 9108, was tested with free air controlled enrichment (FACE) approach to study the responses of photosynthetic pigment content and diurnal variation of flag-leaf photosynthesis to elevated atmospheric CO2 concentration and temperature. Four alternative treatments were designed with two CO2 concentration levels (ambient and elevated 200 μmol·mol-1) and two air temperature regimes (ambient and elevated 1-2 ℃). Diurnal variation of flag-leaf photosynthesis was measured in the middle full stage and the late full stage, and photosynthetic pigment of the leaf was analyzed afterward. Results showed that diurnal variation of net photosynthetic rate (Pn) in each treatment followed a double-peak curve with midday depression feature during late growth stage. Compared to Pn under ambient condition, Pn under elevated CO2 concentration increased by 47.6% and 39.1% on average at middle full stage and late full stage, respectively. There was a negative correlation between temperature and Pn with no significance. Both elevated CO2 concentration and temperature had a significant negative effect on stomatal conductance (gs), decreased by 17.0% and 11.8% on average, respectively. Elevated CO2 concentration significantly reduced transpiration rate (Tr), chlorophyll a (Chl a), chlorophyll b (Chl b), carotene (Car), total chlorophyll (Chl t) and chlorophyll a/b ratio (Chl a/b) during late growth stage of rice by 5.9%, 50.4%, 21.3%, 41.4%, 39.4% and 21.4% on average, respectively, whereas water use efficiency (WUE) increased by 47.9%. However, there were opposite effects on Tr, WUE and photosynthetic pigment content under elevated temperature, with Tr increased by 10.2% and WUE decreased by 20.4%. It could be concluded that elevated CO2 concentration had a greater effect on Pn, gs and photosynthetic pigment content of rice leaf than elevated temperature did during late growth stage. Therefore, it should be paid more attention to the colligate effects of elevated CO2 concentration and high temperature on photosynthesis and photosynthetic pigment content to reduce negative effect of high air temperature.
为研究水稻叶片光合色素和光合日变化对大气CO2浓度和气温升高的响应,我们采用在开放空气中控制升高CO2浓度和温度的方法,以常规粳稻南粳9108为试验材料,设置了环境CO2和高大气CO2浓度(增加200 μmol·mol-1)、环境温度和增温(增加1～2 ℃)交互的4个处理,测定了灌浆中期和后期水稻剑叶的光合日变化特征和光合色素含量.结果表明: 水稻剑叶净光合速率(Pn)为双峰曲线,发生了光合“午休”现象;大气CO2浓度升高提高了剑叶Pn,灌浆中期和后期平均分别增加了47.6%和39.1%;高温有降低Pn的趋势,但相关性未达到显著水平.大气CO2浓度和温度升高导致水稻剑叶生育后期气孔导度(gs)平均分别降低了17.0%和11.8%.高CO2浓度水稻剑叶生育后期蒸腾速率(Tr)、叶绿素a、叶绿素b、类胡萝卜素、总叶绿素和叶绿素a/b值显著降低,平均降幅分别为5.9%、50.4%、21.3%、41.4%、39.4%和21.4%,明显增加了剑叶水分利用率(WUE),平均增幅达47.9%.与之相反,生育后期增温使水稻剑叶Tr增加了10.2%,使WUE平均降低了20.4%.综上所述,大气CO2浓度升高对粳稻生育后期剑叶Pn、gs和光合色素含量的影响明显大于增温效应.因此,应重视大气CO2浓度和温度对水稻光合作用和光合色素的综合效应,减弱增温的负效应.
Keywords: CO 2; diurnal variation of photosynthesis; photosynthetic pigment; rice; temperature.