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).