title: Differential effects of ozone on photosynthesis of winter wheat among cultivars depend on antioxidative enzymes rather than stomatal conductance.
abstract: Five modern cultivars of winter wheat (Triticum aestivum L.): Yangmai16 (Y16), Yangmai 15 (Y15), Yangfumai 2 (Y2), Yannong 19 (Y19) and Jiaxing 002 (J2) were investigated to determine the impacts of elevated ozone concentration (E-O3) on photosynthesis-related parameters and the antioxidant system under fully open-air field conditions in China. The plants were exposed to E-O3at 1.5 times the ambient ozone concentration (A-O3) from the initiation of tillering to final harvest. Pigments, gas exchange rates, chlorophyll a fluorescence, antioxidants contents, antioxidative enzyme activity and lipid oxidation were measured in three replicated plots throughout flag leaf development. Results showed that significant O3effects on most variables were only found during the mid-grain filling stage. Across five cultivars, E-O3significantly accelerated leaf senescence, as indicated by increased lipid oxidation as well as faster declines in pigment amounts and photosynthetic rates. The lower photosynthetic rates were mainly due to non-stomatal factors, e.g. lower maximum carboxylation capacity and electron transport rates. There were strong interactions between O3and cultivar in photosynthetic pigments, light-saturated photosynthesis rate and chlorophyll a fluorescence with O3-sensitive (Y19, Y2 and Y15) and O3-tolerant (J2, Y16) cultivars being clearly differentiated in their responses to E-O3. E-O3significantly influenced the antioxidative enzymes but not antioxidant contents. Significant interactions between O3and cultivar were found in antioxidative enzymes, such as SOD and CAT, but not in stomatal conductance (gs). Therefore, it can be concluded that antioxidative enzymes rather than gsor antioxidants are responsible for the differential responses to E-O3among cultivars. These findings provide important information for the development of accurate modeling O3effects on crops, especially with respect to the developmental stage when O3damage to photosynthesis becomes manifest.
authors.affiliation: State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Shuangqing Road 18, Haidian District, Beijing 100085, China; Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. Electronic address: fzz@rcees.ac.cn.
authors.forename: Zhaozhong
authors.initials: Z
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Shuangqing Road 18, Haidian District, Beijing 100085, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, P.O. Box 461, 40530 Gothenburg, Sweden.
authors.forename: Håkan
authors.initials: H
authors.lastname: Pleijel
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Sciences, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kobayashi
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D010126:Ozone / Q000633:toxicity*; D010788:Photosynthesis / Q000187:drug effects*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D054046:Plant Stomata / Q000187:drug effects / Q000378:metabolism; D014908:Triticum / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics
chemical_list: D000975:Antioxidants; D010126:Ozone
keywords: Air pollution; Antioxidant system; Gas exchange; Ozone; Photosynthesis; Wheat