title: Diurnal variation of apoplastic ascorbate in winter wheat leaves in relation to ozone detoxification.
abstract: Besides stomatal closure, biological detoxification is an important protection mechanism for plants against ozone (O3). This study investigated the diurnal changes of ascorbate (a major detoxification agent) in the apoplast and leaf tissues of winter wheat grown under ambient air field conditions. Results showed the reduced ascorbate in the apoplast (ASCapo) exhibited a peak in late morning or midday, mismatching with either the maximum external O3 concentrations in mid-afternoon or the maximum stomatal O3 uptake between late morning and mid-afternoon. In contrast, the ASC in leaf tissues remained stable throughout the day. The investigations conducted in a Free-Air Concentration Elevation of O3 system confirmed that the diurnal variations of the ASCapo were induced more by the daily variations of O3 concentrations rather than the cumulative O3 effects. In conclusion, the O3-stress detoxification should be a dynamic variable rather than a fixed threshold as assumed in the stomatal flux-based O3 dose metrics.
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, PR China.
authors.forename: Liang
authors.initials: L
authors.lastname: Wang
authors.affiliation: Academy of Resource and Environment, Hubei University, Wuhan 430064, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Pang
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, PR 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 Soil and Sustainable Agriculture, Institute of Soil Sciences, Chinese Academy of Sciences, Nanjing 210008, PR 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: D000393:Air Pollutants / Q000032:analysis* / Q000633:toxicity; D001205:Ascorbic Acid / Q000032:analysis*; D002940:Circadian Rhythm; D008658:Inactivation, Metabolic; D010126:Ozone / Q000032:analysis* / Q000633:toxicity; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism*; D012621:Seasons; D014908:Triticum / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000393:Air Pollutants; D010126:Ozone; D001205:Ascorbic Acid
keywords: Apoplast; Ascorbate; Detoxification; Ozone; Triticum aestivum L