title: Elevated ozone negatively affects photosynthesis of current-year leaves but not previous-year leaves in evergreen Cyclobalanopsis glauca seedlings.
abstract: To assess the effects of leaf age/layer on the response of photosynthesis to chronic ozone (O3), Cyclobalanopsis glauca seedlings, a dominant evergreen broadleaf tree species in sub-tropical regions, were exposed to either ambient air (AA) or elevated O3 (AA + 60 ppb O3, E-O3) for two growing seasons in open-top chambers. Chlorophyll content, gas exchange and chlorophyll a fluorescence were investigated three times throughout the 2nd year of O3 exposure. Results indicated that E-O3 decreased photosynthetic parameters, particularly light-saturated photosynthesis rate, stomatal conductance and effective quantum yield of PSII photochemistry of current-year leaves but not previous-year leaves. Stomatal conductance of plants grown under ambient conditions partially contributed to the different response to E-O3 between leaf layers. Light radiation or other physiological and biochemical processes closely related to photosynthesis might play important roles. All suggested that leaf ages or layers should be considered when assessing O3 risk on evergreen woody species.
authors.affiliation: Key Laboratory of Black Soil Ecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin 150081, China; State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P. O. 2871, Shuangqing Road 18, Haidian District, Beijing 100085, China.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Zhang
authors.forename: Zhaozhong
authors.initials: Z
authors.lastname: Feng
authors.forename: Xiaoke
authors.initials: X
authors.lastname: Wang
authors.forename: Junfeng
authors.initials: J
authors.lastname: Niu
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D002734:Chlorophyll / Q000378:metabolism; D010126:Ozone / Q000633:toxicity*; D010788:Photosynthesis / Q000187:drug effects*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D029963:Quercus / Q000187:drug effects / Q000502:physiology*; D012621:Seasons; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D002734:Chlorophyll; D010126:Ozone
keywords: Chlorophyll a fluorescence; Evergreen tree; Gas exchange; Leaf position; Ozone