A rapid method for determining the fraction of functional Photosystem II in whole leaf tissue after photoinhibition

Assaying functional Photosystem I1 (PSII) complexes by flash-induced oxygen yield from leaf tissue after photoinhibition is most direct but time-consuming, while measurement of chlorophyll fluorescence in leaves is only representative of chloroplast near the leaf surface. To circumvent these deficiencies, we obtained an excellent l linear correlation between (a) the integrated, transient electron flow Σ to PS I, after superimposing a single-turnover flash on steady far-red light, and (b.) the relative oxygen yield per flash during progressive photoinactivation of Photosystem II Leaves of C3 and C4 plants, woody and herbaceous species, wild type and a chlorophyll b-less (PS) II mutant, and monocot and dicot plants gave a single linear correlation, which seems to be a universal relation for predicting the relative oxygen yield per flash from Σ