[Photosynthetic Characteristics and Ozone Dose-response Relationships for Different Genotypes of Poplar].

The open top chambers were used to explore the photosynthetic characteristics of three genotypes of poplar ('546', '90' and '84K') in response to different ozone exposures. The results showed that net photosynthetic rate (), transpiration rate (), water use efficiency (WUE), apparent electron transport rate (ETR), excitation energy capture efficiency of PSⅡ reaction center ('/'), coefficient of photochemical quenching (qP), actual photochemical efficiency of PSⅡ in the light (PhiPS2), chlorophyll a (Chla), chlorophyll b (Chlb), total chlorophyll (Chla+b) and carotenoid (Car)contents were significantly decreased with the increasing ozone concentrations. However, intercellular CO concentration () was significantly increased and stomatal conductance () remained unchanged. There was significant difference in photosynthetic characteristics among three genotypes of poplar. The genotype'546' showed a significant linear correlation (<0.01) between photosynthetic parameters (except ) and the ozone dose index AOT40(accumulated hourly O concentration over a threshold of 40 nmol·mol during daylight hours). Among the three genotypes of poplar, photosynthesis pigments contents in '546' significantly declined with the increase of ozone concentration but not in '90' and '84K'. According to the linear relationship of most photosynthetic parameters and AOT40, especially the total chlorophyll, '546' showed the maximum slope, follows by '90' and then '84K'. So the order of the ozone sensitivity of three poplar genotypes was '546'> '90'> '84K'. The results of this study can provide an important basis for breeding ozone resistant genotype of poplar as well as protecting poplar from ozone damage.