title: A rapid, whole-tissue determination of the functional fraction of PSII after photoinhibition of leaves based on flash-induced P700 redox kinetics.
abstract: Assaying the number of functional PSII complexes by the oxygen yield from leaf tissue per saturating, single-turnover flash, assuming that each functional PSII evolves one oxygen molecule after four flashes, is one of the most direct methods but time-consuming. The ratio of variable to maximum Chl fluorescence yield (F(v)/F(m)) in leaves can be correlated with the oxygen yield per flash during a progressive loss of PSII activity associated with high-light stress and is rapid and non-intrusive, but suffers from being representative of chloroplasts near the measured leaf surface; consequently, the exact correlation depends on the internal leaf structure and on which leaf surface is being measured. Our results show that the average F(v)/F(m) of the adaxial and abaxial surfaces has a reasonable linear correlation with the oxygen yield per flash after varied extents of photoinactivation of PSII. However, we obtained an even better linear correlation between (1) the integrated, transient electron flow (Sigma) to P700+, the dimeric Chl cation in PSI, after superimposing a single-turnover flash on steady background far-red light and (2) the relative oxygen yield per flash. Leaves of C3 and C4 plants, woody and herbaceous species, wild-type and a Chl-b-less mutant, and monocot and dicot plants gave a single straight line, which seems to be a universal relation for predicting the relative oxygen yield per flash from Sigma. Measurement of Sigma is non-intrusive, representative of the whole leaf tissue, rapid and applicable to attached leaves; it may even be applicable in the field.
authors.affiliation: Photobioenergetics Group, Research School of Biological Sciences, Australian National University, Canberra, Australian Capital Territory 0200, Australia.
authors.forename: Pasquale
authors.initials: P
authors.lastname: Losciale
authors.forename: Riichi
authors.initials: R
authors.lastname: Oguchi
authors.forename: Luke
authors.initials: L
authors.lastname: Hendrickson
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Hope
authors.forename: Luca
authors.initials: L
authors.lastname: Corelli-Grappadelli
authors.forename: Wah Soon
authors.initials: WS
authors.lastname: Chow
mesh_terms: D002212:Capsicum / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism*; D007700:Kinetics; D008027:Light; D010084:Oxidation-Reduction; D017440:Photoperiod; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000302:isolation & purification / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; C001785:chlorophyll P 700