title: Allocation of Absorbed Light Energy in Photosystem II in NPQ Mutants of Arabidopsis.
abstract: To analyze changes of energy allocation in PSII at non-steady state photosynthesis, the induction and relaxation of non-photochemical quenching of Chl fluorescence was re-evaluated with the use of Arabidopsis thaliana mutants in which the ability to induce non-photochemical quenching was either enhanced (npq2) or suppressed (npq1 and npq4). When dark-treated leaves of the wild type (WT) were illuminated, very high Φf,D, which represents the loss of excitation energy via non-regulated dissipation, at the beginning of light illumination was gradually decreased to the steady-state level. In contrast, ΦNPQ, representing regulated energy dissipation in PSII, was relatively constant after a significant change in the first 10 min. In npq1 and npq4 mutants, lower ΦNPQresulted in much higher Φf,Dthan in the WT. Comparison of npq1 and npq4 mutants showed a kinetic difference of two types of non-photochemical quenching. Because non-photochemical quenching calculated as NPQ = Fm- Fm')/Fm' was determined by the interplay between ΦNPQand Φf,D, NPQ and ΦNPQ, both of which represent regulatory heat dissipation, were not linearly correlated. We showed that the kinetics of NPQ formation in the light and relaxation in the dark were affected by drastic changes in Φf,DWe discuss the nature of a high level of Φf,Dat the dark-light transition. We also point out an unavoidable problem of applying the energy allocation model when the Fv/Fmvalue changes during a photoinhibiotry illumination.
authors.affiliation: Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto, 606-8502 Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ikeuchi
authors.affiliation: Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto, 606-8502 Japan.
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Sato
authors.affiliation: Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto, 606-8502 Japan tuendo@kais.kyoto-u.ac.jp.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Endo
mesh_terms: D065638:Absorption, Radiation; D000222:Adaptation, Physiological / Q000528:radiation effects; D017360:Arabidopsis / Q000502:physiology* / Q000528:radiation effects*; D002734:Chlorophyll / Q000378:metabolism; D003624:Darkness; D005453:Fluorescence; D008027:Light; D009154:Mutation / Q000235:genetics*; D055668:Photochemical Processes / Q000528:radiation effects; D010788:Photosynthesis / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D013997:Time Factors
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll
keywords: Arabidopsis thaliana; Chlorophyll fluorescence; Energy allocation in PSII; Induction phase of photosynthesis; Non-photochemical quenching (NPQ)