中文摘要：

采用开顶箱气室（OTC）模拟熏蒸法，研究高浓度臭氧（O3）对沈阳市常用绿化树种梓树（Catalpa ovata）生长和光合作用的影响。结果表明： 高浓度臭氧显著抑制了梓树的生长；与对照组（OA）相比，160 nmol·mol-1 O3处理20 d后，梓树叶片的相对含水量、干重、鲜重、比叶重、干重增量、鲜重增量均显著下降（P〈0.05）；梓树叶片净光合速率（Pn）随O3处理时间延长逐渐降低，胞间CO2浓度（Ci）和蒸腾速率（Tr）与气孔导度（Gs）的变化趋势一致，表现为先降低后升高的趋势，高浓度O3对梓树叶片Pn的降低主要是由非气孔因素限制引起；高浓度O3处理后，梓树叶片光合系统受损，发生光抑制现象，PSⅡ最大光化学效率（Fv/Fm）和PSⅡ电子传递量子产率（ΦPSⅡ）随着处理时间的延长而显著下降（P〈0.05）；梓树叶片超氧化物歧化酶（SOD）和抗坏血酸过氧化物酶（APX）活性在高浓度O3处理下呈下降趋势，表明梓树抗氧化系统无法承受高浓度的臭氧胁迫，2种抗氧化酶在短期O3胁迫下都未能做出积极的生理响应。

英文摘要：

By using opentop chambers （OTCs）, this paper studied the effects of elevated O3 concentration on the growth and photosynthesis of Catalpa ovata, a common greening tree species in Shenyang City. The results showed that elevated O3 concentration significantly inhibited the growth of C. ovata. Compared to the ambient air control, relative water content, dry weight, fresh weight, specific leaf weight, dry weight increment and fresh weight increment were significantly decreased in leaves of C. ovata after 20 days exposure to O3 （160 nmol·mol-1）. The net photosynthetic rate （Pn） of C. ovata gradually decreased with the extension of time. The decrease in photosynthesis of C. ovata was related to nonstomatal factors. The change trends of intercellular CO2 concentration （Ci） and transpiration rate （Tr） and stomatal conductance （Gs） were consistent, with decline first and then increase. The maximal photochemistry efficiency of PSⅡ （Fv/Fm） and quantum yield of PSⅡ electron transport （ΦPSⅡ） decreased significantly over the time （P〈0.05）, the decline of C. ovata photosynthesis correlated markedly with the excess of light energy, and photoinhibition phenomenon under O3 stress. Superoxide dismutase （SOD） and ascorbic acid peroxidase （APX） activities showed no significant change during the whole O3 stress, which implied that it was quite difficult for C. ovata to tolerate excessive O3 concentration, and two antioxidant enzymes did not make positive physiological response to the acute stress of O3.