tailieunhanh - Báo cáo khoa học: Quantitative analysis of the experimental O–J–I–P chlorophyll fluorescence induction kinetics Apparent activation energy and origin of each kinetic step Steve Boisvert, David Joly and Robert Carpentier

Fluorescence induction has been studied for a long time, but there are still questions concerning what the O–J–I–P kinetic steps represent. Most stud-ies agree that the O–J rise is related to photosystem II primary acceptor (QA) reduction, but several contradictory theories exist for the J–I and I–P rises. | ễFEBS Journal Quantitative analysis of the experimental O-J-I-P chlorophyll fluorescence induction kinetics Apparent activation energy and origin of each kinetic step Steve Boisvert David Joly and Robert Carpentier Groupe de Recherche en Biologie Vegetale GRBV Universite du Quebec a Trois-Rivières Quebec Canada Keywords chlorophyll fluorescence DCMU photosystem II plastoquinone thylakoid Correspondence R. Carpentier Groupe de Recherche en Biologie Vegetale GRBV Universite du Quebec a Trois-Rivieres Trois-Rivieres Quebec Canada G9A 5H7 Fax 1 819 376 5057 E-mail Received 17 May 2006 revised 10 July 2006 accepted 22 August 2006 doi Fluorescence induction has been studied for a long time but there are still questions concerning what the O-J-I-P kinetic steps represent. Most studies agree that the O-J rise is related to photosystem II primary acceptor Qa reduction but several contradictory theories exist for the J-I and I-P rises. One problem with fluorescence induction analysis is that most work done to date has used only qualitative or semiquantitative data analysis by visually comparing traces to observe the effects of different chemicals or treatments. Although this method is useful to observe major changes a quantitative method must be used to detect more subtle yet important differences in the fluorescence induction trace. To achieve this we used a relatively simple mathematical approach to extract the amplitudes and half-times of the three major fluorescence induction phases obtained from traces measured in thylakoid membranes kept at various temperatures. Apparent activation energies Ea were also obtained for each kinetic step. Our results show that each phase has a different EA with EA O-J Eaj-i Ea i-p and thus a different origin. The effects of two well-known chemicals 3- 3 4-dichlorophenyl -1 1-dimethylurea which blocks electron transfer to the photosystem II secondary electron acceptor Qb and .