水分胁迫和高浓度CO_(2)处理下水稻幼苗光合生理响应特征

Photosynthetic physiological response of rice seedlings to water stress and high CO_(2)concentration

试验以水稻(Oryza sativa L.)品种“辽星一号”为材料,在不同CO_(2)浓度(380±10μmol·mol^(-1),760±20μmol·mol^(-1))下,利用PEG⁃6000模拟根系水分胁迫(PEG⁃6000浓度为0、5%、10%和15%),通过对光合参数测定,研究高浓度CO_(2)和水分胁迫对水稻幼苗光合生理影响,为阐明植物如何应对复杂环境变化提供理论依据。结果表明:单一水分胁迫抑制水稻幼苗的生长,株高、根长、鲜重和干重显著降低,且对地上部分的抑制作用大于地下部分,对鲜重的抑制作用大于干重;净光合速率(P_(n))、气孔导度(G_(s))和蒸腾速率(Tr)显著低于对照,轻度(5%)和中度(10%)水分胁迫下胞间CO_(2)浓度(Ci)显著低于对照,P_(n)的降低主要由气孔因素决定,重度(15%)水分胁迫下Ci显著高于对照,P_(n)的降低主要由非气孔因素决定;叶绿体色素含量(Chla、Chlb、Car)、初始荧光产量(F_(o))、PSII最大光化学量子产量(F_(v)/F_(m))及潜在光化学效率(F_(v)/F_(o))在轻度水分胁迫下未发生显著变化;中度水分胁迫下F_(o)无显著变化,重度胁迫下F_(o)显著提高,中度、重度胁迫下,F_(v)/F_(m)、F_(v)/F_(o)和Chla、Chlb、Car显著降低;与对照比较,单独高浓度CO_(2)促进水稻幼苗生长,株高和根长显著增加,且对根长的促进作用大于株高,对干重的促进作用大于鲜重,使地下部分干重显著增加;高浓度CO_(2)显著增加P_(n),显著降低G_(s)、Tr和Ci,且通过提高F_(v)/F_(m)、F_(v)/F_(o)及叶绿体色素含量提高光合作用;复合处理与单一水分胁迫比较,高浓度CO_(2)促进水稻幼苗生长,也使水分胁迫下P_(n)、G_(s)和Tr显著升高,通过降低F_(o),提高F_(v)/F_(m)、F_(v)/F_(o)及叶绿体色素含量促进光合作用,减轻水分胁迫对水稻幼苗的伤害,使重度水分胁迫P_(n)下降由非气孔因素转化为气孔因素。

In this study,rice(Oryza sativa L.)cultivar“Liao Star 1”was used as the material to examine the effects of high CO_(2)concentration and drought stress on photosynthetic physiology of rice seedlings under CO_(2)con⁃centrations of 380±10 and 760±20μmol·mol^(-1),aiming to provide a theoretical basis for explaining how plants cope with complex environmental changes.PEG⁃6000(0,5%,10%,and 15%)was used to simulate rhizosphere drought stress.Single drought stress inhibited the growth of rice seedlings,decreased plant height,root length,fresh weight and dry weight,with stronger inhibitory effect on aboveground part than that on underground part,and on fresh weight than on dry weight.Under drought stress,net photosynthetic rate(P_(n)),stomatal conductance(G_(s))and transpiration rate(Tr)were significantly decreased compared with the control.Under light(5%)and moderate(10%)drought stress,intercellular CO_(2)concentration(Ci)decreased,and the decrease of Pnwas largely due to stomatal factors.Under severe(15%)drought stress,Ci increased,and the decrease of P_(n)was largely due to non⁃stomatal factors.The chloroplast pigment contents,initial fluorescence yield(F_(o)),largest PSII photo⁃chemical quantum yield(F_(v)/F_(m)),and potential photochemical efficiency(F_(v)/F_(o))did not change significantly under mild drought stress.F_(o)did not change significantly under moderate drought stress,but significantly increased under severe drought stress.Under moderate and severe drought stress,F_(v)/F_(m),F_(v)/F_(o)and Chla,Chlb,Car contents were significantly decreased.Compared with the control,high CO_(2)concentration alone promoted the growth of rice seed⁃lings,plant height and root length,with stronger promotion effect on root than plant height.The dry weight of un⁃derground part increased significantly due to its promoting effect on dry weight than fresh weight.High CO_(2)concen⁃tration significantly increased P_(n),and decreased G_(s),Tr and Ci.Photosynthesis was also increased by the increases of F_(v)/F_(m),F_(v)/F_(o)and Chla,Chlb,Car contents.Under high CO_(2)and water stress,high CO_(2)promoted the growth of rice seedlings compared with water stress alone,P_(n),G_(s) and Tr were also significantly increased.Photosynthesis was promoted by the increases of F_(v)/F_(m),F_(v)/F_(o)and contents of chlorophyll and decrease of F_(o),and thus reduced dam⁃age induced by water stress.The decrease of P_(n)under severe water stress transformed from non⁃stomatal factors to stomatal factors.