中文摘要：

以沈阳市2个主要树种白桦（Betula platyphylla）、银中杨（Populus alba×P.berolinensi）1年生植株为对象,利用开顶箱（OTCs）模拟法,研究了高浓度O3（约160 nmol·mol-1）对2树种叶片光合作用的影响。结果表明：与对照相比,高浓度O3熏蒸的植株叶片出现坏死斑等伤害症状,熏蒸14和30 d时,白桦单叶伤害面积分别为72.0%和91.6%,显著高于银中杨的21.5%和26.2%（P〈0.01）。白桦叶片Chl-a和Car含量显著降低,银中杨的Chl-b含量显著上升（P〈0.05）。2树种叶片的离子渗漏率和丙二醛（MDA）含量均显著增加（P〈0.05）,超氧化物歧化酶（SOD）和抗坏血酸过氧化物酶（APX）活性均显著降低（P〈0.05）。高浓度O3导致2树种净光合速率（Pn）下降,胞间CO2浓度（Ci）上升,但银中杨气孔导度（Gs）增加,而白桦的降低。推断O3导致2树种光合作用降低是由非气孔因素限制引起,高浓度O3熏蒸下银中杨耐性较白桦强,白桦可以作O3的指示树种。

英文摘要：

One-year-old seedlings of two main tree species（ Betula platyphylla,Populus alba ×P. berolinensi） in Shenyang were exposed to high O3concentration（ about 160 nmol·mol-1） in open-top chambers（ OTCs） and its effect on photosynthesis in leaves of the two tree species was studied. The results showed that the foliage of both species showed necroses induced by the elevated O3. After 14 and 30 d exposures of elevated O3,the percentages of visible foliar injury per leaf in B. platyphylla were 72. 0% and 91. 6%,significantly higher than that in leaf of P. alba× P. berolinens,which were 21. 5% and 26. 2%（ P 〈 0. 01）. Chl-a and Car contents decreased significantly in B. platyphylla,but Chl-b content increased in P. alba × P. berolinensi（ P 〈 0. 05）. Electrolyte leakage and malondialdehyde（ MDA） contents were significantly increased in leaves of the two tree species（ P 〈 0. 05）,while superoxide dismutase（ SOD） and ascorbic acid peroxidase（ APX） activities decreased significantly（ P 〈 0. 05）. The net photosynthetic rate（ Pn） was decreased significantly and intercellular CO2concentration（ Ci） was significantly increased in the two tree species（ P 〈 0. 05）,but stomatal conductance（ Gs） increased in P. alba × P. berolinensi and decreased slightly in B. platyphylla. We infer that the decrease in photosynthesis of the two tree species is related to non-stomatal factors. P. alba × P. berolinensi has higher tolerance to high O3 concentration than B. platyphylla,and B. platyphylla can be considered as an O3 indicator species.