An indoor simulation experiment was performed by controlling the different temperature and soil water conditions to study the single and combined stress of elevated temperature and drought on photosynthetic characteristics,chlorophyll fluorescence and the antioxidant enzymes activities in Populus×'Nanlin-895'seedling leaves.As the stress time progressed,net photosynthetic rate (Pn),stomatal conductance (Gs),transpiration rate (Tr),maximal fluorescence (Fm),optimal/ maximal photochemical efficiency of PS Ⅱ (Fv/Fm) of Poplar seedlings were decreased,whereas,minimal fluorescence (Fo) was increased under the single or combined stress of elevated temperature and drought.Intercellular CO2 concentration (Ci) and water use efficiency (WUE) were decreased first and increased,and the activities of superoxide dismutase (SOD) and peroxidase (POD) had the opposite trend under the moderate stress of drought.Activities of superoxide dismutase (SOD) and peroxidase (POD) were decreased significantly under the severe stress of elevated temperature or their combination at the end of stress time.Decreases in net photosynthetic rate (Pn) were the result of stomatal and non-stomatal limitation under moderate stress of elevated temperature or drought,while the result of non-stomatal limitation was under the severe stress of elevated temperature or drought or their combination.The combined stress showed synergistic effects on Pn and Tr.The effects of the combined stress on Pn,Gs,Ci,Tr,Fv/Fm and SOD were higher than that of a single stress,and poplar seedlings suffered the worst under the combined stress of elevated temperature and drought.%采用室内模拟试验,研究了高温、干旱单一或复合胁迫对南林895杨(PopulusבNanlin-895’)幼苗光合特性、叶绿素荧光、抗氧化酶活性的影响.结果表明:随着胁迫时间的延长,高温、干旱单因子和复合胁迫使杨树幼苗净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、最大荧光(Fm)、PSII最大原初光化学量子效率(F、/Fm)下降、初始荧光(F.)升高,中度干旱胁迫使胞间CO2摩尔分数(Ci)、水分利用效率(WUE)先降后升,超氧化物歧化酶(SOD)、过氧化物酶(POD)活性先升后降,Pn主要受气孔和非气孔因素共同限制;重度高温、重度干旱和复合胁迫末期SOD 、POD活性下降显著,Pn主要受非气孔因素限制.复合胁迫对Pn、Tr具有叠加效应.复合胁迫对Pn、Gs、Ci、T、F/Fm、SOD的胁迫效应大于单一胁迫;杨树幼苗在高温和干旱复合胁迫条件下受害最严重.
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