Response of diurnal variation in photosynthesis to elevated atmospheric CO_2 concentration and temperature of rice between cloudy and sunny days: a free air CO_2enrichment study
人类活动导致大气二氧化碳浓度(CO_2)升高、全球气候变暖和光合有效辐射(PAR)降低,影响着绿色作物的光合作用。为了明确高CO_2浓度、高温和低PAR对水稻光合日变化特征的影响,利用中国稻田开放空气CO_2浓度升高系统(free air CO_2 enrichment,FACE),以常规粳稻南粳9108为试验材料,设置了环境CO_2和高CO_2浓度(增200mumol/mol)、环境温度和增高温度(增12℃)交互的4个处理,从9:00到17:00每隔1h测定了阴天和晴天水稻的光合作用,研究了不同天气对水稻光合日变化对大气CO_2浓度和温度升高的响应。观察到不同天气条件下水稻光合日变化的不同特征,晴天Pn为双峰曲线,发生了光合午休,阴天未发生。结果表明,高CO_2浓度显著提高了水稻Pn,温度升高有降低水稻Pn趋势,CO_2浓度增加200mumol/mol对水稻光合作用的促进效应远大于增温12℃对其的抑制效应。高CO_2浓度显著增加了水稻胞间CO_2浓度(Ci),降低了水稻蒸腾速率(Tr),平均降幅为10.8%22.0%。高温有降低Ci的趋势,增加了Tr,平均增幅达5.0%13.5%。晴天比阴天增加了水稻Tr,平均增幅为9.8%31.2%。CO_2浓度和温度同时升高显著降低了水稻气孔导度(Gs)。这些结果说明CO_2浓度、温度和PAR对水稻水分利用率(WUE)产生综合影响。阴天PAR比晴天平均低53.3%,阴天水稻Pn比晴天显著低,平均降幅达37.1% 72.0%。与对照比较,高CO_2浓度处理,较高PAR(晴天)条件下水稻Pn的增幅(38.6%58.4%)显著大于较低PAR(阴天)条件下水稻Pn的增幅(21.6%38.8%),这一现象值得关注和深入探讨。研究结果表明,评估气候变化对水稻生产的影响,需同时考虑未来大气CO_2浓度和温度升高以及PAR下降的因素及其相互作用。
英文摘要:
To understand the effect of elevated CO_2 concentration,temperature,and different weather of photosynthetically active radiation (PAR) on diurnal variation photosynthetic characteristics of rice,a paddy field experiment utilizing free air CO_2 enrichment (FACE) technology was conducted at two concentration levels of CO_2 (ambient and elevated 200mumol/mol) and two temperature regimes (ambient and elevated 12℃) between cloudy and sunny days,using the widely cultivated inbred Japonica rice (Oryza sativa L.) Nanjing 9108 as the test material. Diurnal variation in the photosynthetic characteristics of rice were measured every hour from 9:00 to 17:00 in the two kinds of weather. The diurnal variations in net photosynthetic rate (Pn) under each treatment followed a single-peak curve during cloudy days without a midday depression in photosynthesis,and a double-peak curve during sunny days with a midday depression. The results showed that elevated atmospheric CO_2 concentrations significantly increased rice Pn. However,elevated temperature tended to reduce Pn. Therefore,elevating atmospheric CO_2 concentration by 200mumol/mol had a greater effect on the photosynthetic characteristics of rice than elevating temperature by 12℃. Elevated CO_2 concentration improved rice intercellular CO_2 concentration (Ci) and inhibited transpiration rate (Tr) by an average 10.8%22.0%. Elevated temperature nonsignificantly decreased Ci and increased Tr by an average 5.0%13.5%. Rice Tr on sunny days was larger than on cloudy days,by an average of 9.8%31.2%. Rice stomatal conductance (Gs) decreased significantly under elevated CO_2 concentrations and temperature. This indicated that CO_2 concentration,temperature,and PAR had a comprehensive effect on rice water use efficiency (WUE). The PAR on cloudy days was 53.3% lower than on sunny days. At the same time,the average Pn on cloudy days was lower by an average of 37.1%72.0% than that on sunny days. Compared with ambient conditions,Pn increased under elevated CO_2 concentrations average by 21.6%38.8% and 38.6%58.4% in the low PAR of cloudy days and in the high PAR of sunny days,respectively. It is suggested that more attention should be focused on the effect of elevated CO_2 concentration,elevated temperature,and the downward trend of PAR on rice,which would be conducive to a more comprehensive assessment of climate change impacts on rice production.