title: Rate Constants of PSII Photoinhibition and its Repair, and PSII Fluorescence Parameters in Field Plants in Relation to their Growth Light Environments.
abstract: The extent of photoinhibition of PSII is determined by a balance between the rate of photodamage to PSII and that of repair of the damaged PSII. It has already been indicated that the rate constants of photodamage (kpi) and repair (krec) of the leaves differ depending on their growth light environment. However, there are no studies using plants in the field. We examined these rate constants and fluorescence parameters of several field-grown plants to determine inter-relationships between these values and the growth environment. The kpi values were strongly related to the excess energy, EY, of the puddle model and non-regulated energy dissipation, Y(NO), of the lake model, both multiplied by the photosynthetically active photon flux density (PPFD) level during the photoinhibitory treatment. In contrast, the krec values corrected against in situ air temperature were very strongly related to the daily PPFD level. The plants from the fields showed higher NPQ than the chamber-grown plants, probably because these field plants acclimated to stronger lightflecks than the averaged growth PPFD. Comparing chamber-grown plants and the field plants, we showed that kpi is determined by the incident light level and the photosynthetic capacities such as in situ rate of PSII electron transport and non-photochemical quenching (NPQ) [e.g. Y(NO)×PPFD] and that krec is mostly determined by the growth light and temperature levels.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Miyata
authors.affiliation: The University Museum, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ikeda
authors.affiliation: Makino Herbarium, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Ohsawa, Hachioji, Tokyo, 192-0397 Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nakaji
authors.affiliation: National Herbarium and Plant Laboratories, Department of Plant Resources, Godawari, Nepal.
authors.forename: Dhana Raj
authors.initials: DR
authors.lastname: Kanel
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan itera@bs.s.u-tokyo.ac.jp.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Terashima
mesh_terms: D018553:Cucumis sativus / Q000254:growth & development / Q000528:radiation effects; D004777:Environment; D005453:Fluorescence; D007564:Japan; D007700:Kinetics; D008027:Light; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D063245:Plant Development / Q000528:radiation effects*; D010944:Plants / Q000378:metabolism / Q000528:radiation effects*; D013816:Thermodynamics
chemical_list: D045332:Photosystem II Protein Complex
keywords: Chlorophyll fluorescence; Excess energy hypothesis; Jaljale Himal; Non-regulated energy dissipation; Photoinhibition; Two-step hypothesis