大气CO_(2)浓度和气温升高对大豆叶片光合特性及氮代谢的影响

Effects of Elevated Atmospheric CO_(2)Concentration and Increased Air Temperature on Photosynthetic Characteristics and Nitrogen Metabolism of Soybean Leaves

以大豆品种“中黄35”为材料,利用人工气候室,设置对照CK(CO_(2)浓度和气温与外界测定值相同)、EC(CO_(2)浓度为外界测定值+200μmol·mol–1,气温与外界测定值相同)、ET(CO_(2)浓度与外界测定值相同,气温为外界测定值+2℃)、ECT(CO_(2)浓度为外界测定值+200μmol·mol–1,气温为外界大气测定值+2℃)共4个处理。大豆整个生育期均种植在人工气候室内,在大豆鼓粒期(8月12日)利用相对叶绿素仪测定大豆叶片相对叶绿素含量,利用便携式气体交换系统测定光合参数,利用便携式光合测量系统测定光响应曲线和CO_(2)响应曲线,并测定叶片氮代谢相关指标,以研究CO_(2)浓度升高200μmol·mol–1和气温升高2℃对鼓粒期大豆叶片的光合特性和氮代谢关键指标的影响。结果表明:(1)ET处理鼓粒期大豆叶片相对叶绿素含量(SPAD)显著增加,EC和ECT处理对其影响不明显。(2)各处理鼓粒期大豆叶片气孔导度(Gs)均显著下降。ET处理中,叶片净光合速率(Pn)、水分利用效率(WUE)显著下降,EC处理对其影响不大,但是可以提高叶片水分利用效率(WUE),改善气温升高对叶片的负面影响。(3)EC和ET处理鼓粒期大豆叶片最大净光合速率(Pnmax)均显著下降,ECT处理对其影响不显著。(4)EC处理中,鼓粒期大豆叶片CO_(2)补偿点(Γ)、饱和胞间CO_(2)浓度(Cisat)、光呼吸速率(Rp)均显著增加,ET和ECT对其影响不大。各处理均使鼓粒期大豆叶片最大净光合能力(Amax)下降。(5)EC处理鼓粒期大豆叶片硝酸还原酶(NR)活性和可溶性蛋白含量均显著下降,但是ET和ECT处理叶片可溶性蛋白含量显著增加,硝酸还原酶(NR)活性变化不显著,各处理均降低了谷氨酰胺合成酶(GS)的活性。总之,CO_(2)浓度升高200μmol·mol–1可以改善气温升高2℃对鼓粒期大豆叶片光合作用的负面影响,但对氮代谢有抑制作用,而气温升高2℃可以一定程度上缓解CO_(2)浓度升高200μmol·mol–1对鼓粒期大豆叶片氮代谢的抑制作用。

The effects of elevated CO_(2)concentration and increased temperature on photosynthetic characteristics and nitrogen metabolism of soybean leaves were studied in order to provide reference for soybean production under climate change in the future.In this experiment,soybean variety‘Zhonghuang35’was used as the test material.The experiment was carried out at four treatments:CK(the CO_(2)concentration and air temperature were consistent with atmosphere measurement value),EC(the CO_(2)concentration is the measured value in the atmosphere+200μmol·mol–1;the air temperature was consistent with atmosphere measurement value),ET(the CO_(2)concentration was consistent with atmosphere measurement value;the air temperature was the measured value in the atmosphere+2℃),and ECT(the CO_(2)concentration was the measured value in the atmosphere+200μmol·mol–1 and the air temperature was the measured value in the atmosphere+2℃).The soybean was planted in the artificial climate chamber throughout the growth period.At the seed filling stage of soybean,we measured the relative chlorophyll content of soybean leaves by leaf chlorophyll meter,photosynthetic parameters by portable gas exchange system,light response curves and CO_(2)response curves by portable photosynthesis measurement system,and measured the leaf nitrogen metabolism related indeices,through these experiment results to study the effect of CO_(2)concentration elevated by 200μmol·mol–1 and air temperature increased by 2℃on photosynthetic characteristics and key indicators of nitrogen metabolism of soybean leaves at seed filling stage.The results showed that:(1)ET treatment significantly increased the relative chlorophyll content(SPAD)of soybean leaves at seed filling stage,but EC treatment and ECT treatment had no significant effect on SPAD.(2)The stomatal conductance(Gs)of soybean leaves at seed filling stage was decreased significantly in all treatments.Net photosynthetic rate(Pn)and water use efficiency(WUE)of leaves was decreased significantly in ET treatment.EC treatment had little effect on Gs of soybean leaves,but it could improve WUE of soybean leaves and alleviate the negative effect of ET treatment.(3)EC treatment and ET treatment significantly decreased the maximum net photosynthetic rate(Pnmax)of soybean leaves at seed filling stage,but ECT treatment had no significant effect on it.(4)In EC treatment,CO_(2)compensation point(Γ),saturated intercellular CO_(2)concentration(Cisat)and photorespiration rate(RP)of soybean leaves were significantly increased,but ET treatment and ECT treatment had little effect on them all treatments decreased the maximum net photosynthetic capacity(Amax)of soybean leaves at seed filling stage.(5)The nitrate reductase(NR)activity and soluble protein content of soybean leaves was decreased significantly in EC treatment,while the soluble protein content of soybean leaves was increased significantly in ET treatment and ECT treatment,but NR activity and glutamine synthetic(GS)activity was not significantly changed.In conclusion,in this experiment,elevated CO_(2)concentration by 200μmol·mol–1alleviated the negative effect of increased air temperature by 2℃on photosynthesis of soybean leaves at seed filling stage,but the nitrogen metabolism was inhibited.Increased air temperature by 2℃can alleviate the inhibition of CO_(2)concentration by 200μmol·mol–1 on nitrogen metabolism to a certain extent.