2.6.1. Measurement of PSII activity (JIP-Test)
To check the PSII performance, Chl a fluorescence measurements [Structural and functional heterogeneity: (i) antenna heterogeneity is related with QA reduction when electron flow to PQ pool or (ii) reducing side (functioning of reduction side i.e. QBˉ reducing and non-reducing centres): (a) oxidation/ reduction rate of PQ (Fo/Fm ), (b) efficiency of water splitting complex (Fo/Fv ), (c) fluorescence yields ratio for open and closed states (Fm/Fo ) and size and number of active reaction centres (Fv/Fo );Technical parameters: (i) initial fluorescence (Fₒ ), (ii) variable fluorescence (Fᵥ ), (iii) maximum fluorescence (Fm ), (iv) QA redox turnover number until Fm is reached (N ) and (v) size of plastoquinone (PQ) pool i.e. area beyond the fluorescence induction curve between Fo andFm (Area ); Quantum yields and efficiencies: (i) probability of an electron movement by trapped exciton into electron transport chain beyond QAˉ (yield of electron transport per trapped exciton; Psi_oor Ψo ), (ii) quantum yield of primary photochemistry (Phi_Po orФPo ), (iii) probability of dissipation of an absorbed photon (ФDo ) and (iv) quantum yield of electron transport (Phi_Eo orФEo ); Specific energy fluxes: (i) absorption of PSII antenna Chls shared by number of active RC (QA reduction) (ABS/RC; denotes antenna size), (ii) trapped energy flux per active RC [denotes only active RCs (QA‒QAˉ);TRo/RC ], (iii) electron transport flux per active RC (from QAˉ to PQ;ETo/RC ), (iv) dissipation amount of active RCs (DIo/RC ) and (v) energy needed to close all the RCs (Sm ); Overall performance index(PIABS )] were carried out in the dark adapted cyanobacterial samples by using hand held fluorometer (AquaPen AP 100, Photon System Instruments, Czech Republic) following the method of Strasser et al. (2000).