Kinetics of prolonged photoinhibition revisited: photoinhibited Photosystem II centres do not protect the active ones against loss of oxygen evolution |
| |
Authors: | Päivi Sarvikas Taina Tyystjärvi Esa Tyystjärvi |
| |
Institution: | (1) Plant Physiology and Molecular Biology, Department of Biology, University of Turku, 20014 Turku, Finland; |
| |
Abstract: | Photoinhibition of Photosystem II (PSII) in lincomycin-treated leaves begins as a first-order reaction, but fluorescence measurements
have suggested that after prolonged illumination, the number of active PSII centres stabilizes to 15–20% of control. The stabilization
has been interpreted to indicate that photoinhibited PSII centres protect the remaining active centres against photoinhibition
(Lee, Hong and Chow, Planta 212:332–342, 2001). In an attempt to study the mechanism of this protection, we measured the reaction
kinetics of photoinhibition in lincomycin-treated pumpkin (Cucurbita pepo L.) and pepper (Capsicum annuum L.) leaves in vivo. The light-saturated rate of PSII oxygen evolution, assayed from thylakoids and isolated from the treated
leaves, was used as a direct measure of the number of remaining active PSII centres, and the fluorescence parameters F
V/F
M and (F
V/F
M)/F
0 (=1/F
0 − 1/F
M) were measured for comparison. To our surprise, no stabilization of PSII activity was observed and photoinhibition followed
first-order kinetics until PSII activity had virtually declined to zero. A series of in vitro experiments was carried out
to see whether stabilization of PSII activity occurs if a particular combination of light intensity and wavelength range is
applied, or if a specific PSII preparation is used as experimental material. The results of the in vitro experiments confirmed
the in vivo result about persistent first-order kinetics. We conclude that photoinhibited PSII centres offer no measurable
protection against photoinhibition. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|