title: The photoprotective role of epidermal anthocyanins and surface pubescence in young leaves of grapevine (Vitis vinifera).
abstract: OBJECTIVE
  Depending on cultivar, surfaces of young leaves of Vitis vinifera may be glabrous-green ('Soultanina') or transiently have anthocyanins ('Siriki') or pubescence ('Athiri'). A test is made of the hypothesis that anthocyanins and pubescence act as light screens affording a photoprotective advantage to the corresponding leaves, and an assessment is made of the magnitude of their effect.
  
  
  METHODS
  Measurements were made on young leaves of the three cultivars in spring under field conditions. Photosynthetic gas-exchange and in vivo chlorophyll fluorescence were measured. Photosynthetic and photoprotective pigments were analysed by HPLC.
  
  
  RESULTS
  Compared with glabrous-green leaves, both anthocyanic and pubescent leaves had greater dark-adapted PSII photochemical efficiency and net photosynthesis. In leaves possessing either anthocyanins or pubescence, the ratio of xanthophyll cycle components to total chlorophyll, and mid-day de-epoxidation state of the xanthophyll cycle were considerably smaller, than in glabrous-green leaves. These differences were more evident in pubescent leaves, probably indicating that trichomes were more effective in decreasing light stress than anthocyanins in the epidermis.
  
  
  CONCLUSIONS
  Light screens, especially in the form of pubescence, decrease the risk of photoinhibition whilst allowing leaves to maintain a smaller content of xanthophyll cycle components and depend less on xanthophyll cycle energy dissipation. This combination of photoprotective features, i.e. decreased photon flux to the photosynthetic apparatus and lower xanthophyll cycle utilization rates may be particularly advantageous under stressful conditions.
authors.affiliation: Laboratory of Plant Physiology, Department of Agricultural Biotechnology, Agricultural University of Athens, Iera Odos 75, 118 55, Botanikos, Athens, Greece. g_liak@aua.gr
authors.forename: Georgios
authors.initials: G
authors.lastname: Liakopoulos
authors.forename: Dimosthenis
authors.initials: D
authors.lastname: Nikolopoulos
authors.forename: Aspasia
authors.initials: A
authors.lastname: Klouvatou
authors.forename: Kornilios-Andrianos
authors.initials: KA
authors.lastname: Vekkos
authors.forename: Yiannis
authors.initials: Y
authors.lastname: Manetas
authors.forename: George
authors.initials: G
authors.lastname: Karabourniotis
mesh_terms: D000872:Anthocyanins / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism / Q000502:physiology; D002851:Chromatography, High Pressure Liquid; D005453:Fluorescence; D008027:Light; D010788:Photosynthesis / Q000502:physiology; D019441:Plant Epidermis / Q000254:growth & development; D018515:Plant Leaves / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism; D027843:Vitis / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism
chemical_list: D000872:Anthocyanins; D002734:Chlorophyll; D002245:Carbon Dioxide