Chlorophyll Fluorescence Parameters: The Definitions, Photosynthetic Meaning, and Mutual Relationships

Chlorophyll fluorescence parameters (Chl FPs) derived from the slow (long-term) induction kinetics of modulated Chl a fluorescence are reviewed and analysed with respect to their application in photosynthesis research. Only four mutually independent Chl FPs, calculated from values of five essential Chl fluorescence (ChlF) yields, are distinguished as the basic ones. These are: the maximum quantum yield of PS2 photochemistry (ΦPO), the photochemical quenching of variable ChlF (qP), the non-photochemical quenching of variable ChlF (qN), and the relative change of minimum ChlF (qO). ΦPO refers to the dark-adapted state of a thylakoid membrane, qP, qN and qO characterise the light-adapted state. It is demonstrated…