ABS/CS0	absorbed photon flux per excited cross-section of PSII (or also apparent antenna size) at t = 0
ABS/RC	average absorbed photon flux per PSII reaction center
DI0/RC	the flux of energy dissipated per active RC
ET0/RC	electron transport flux from QA− to PQ per active PSII
TR0/RC	maximum trapped exciton flux per active PSII
RE0/RC	electron transport flux from QA− to final PSI acceptors per active PSII
Sm	the normalized area between the OJIP curve and the line Fm (a proxy of the number of electron carriers per electron transport chain)—representing energy necessary for the closure of all reaction centers
N	the number indicating how many times QA is reduced while fluorescence reaches its maximal value (number of QA redox turnovers until Fm is reached)
CS	CS, a cross-section of PSII
VL	relative variable fluorescence at L-band
VK	relative variable fluorescence at 300 μs (K-step)
VJ	relative variable fluorescence at 2 ms (J-step)
VI	relative variable fluorescence at 30 ms (I-step)
VK/VJ	the ratio of variable fluorescence in time 0.3 ms to variable fluorescence in time 2 ms as an indicator of the PSII donor side limitation
ΔV/Δto	initial slope (in ms-1) of O-J (the rate of accumulation of closed reaction centers), a ratio expressing the rate of accumulation of closed reaction centers
F0	initial fluorescence value
Fm	maximal fluorescence intensity
FV	variable chlorophyll fluorescence (Fm − Fo)
FV/F0	the ratio between the rate constants of photochemicaland nonphotochemical deactivation of excited Chl molecules
FV/FM	the maximum quantum efficiency of PSII under dark adaptation
φP0	the maximum quantum yield of primary PSII photochemistry
ψE0	the efficiency with which a PSII-trapped electron is transferred from QA to QB
φE0	the quantum yield of electron transport from QA− to PQ
ψR0	the efficiency with which a PSII trapped electron is transferred to final PSI acceptors
φR0	the quantum yield of electron transport from QA− to final PSI acceptors
δR0	the efficiency with which an electron from QB is transferred to the final PSI acceptors
φD0	quantum yield of energy dissipation in PSII antenna (maximum quantum yield of nonphotochemical deexcitation)
PIABS	performance index (potential) for energy conservation from exciton to reduction of intersystem electron acceptors
PITOT	performance index (potential) for energy conservation from exciton to reduction of PSI end acceptors; QA and QB, primary and secondary quinone electron acceptors
SFIABS	PSII structure-function index
PQ	the pool of free plastoquinones
PQH2	Plastoquinols
PC	plastocyanins
PSI	Photosystem I
PSII	Photosystem II
OEC	oxygen-evolving complex
DF	daughter frond
MF	mother frond
GDF	granddaughter frond
MRt	modulated 820-nm reflection intensity at time t
Vox	the rate of P700 oxidation
Vred	the rate of P700 re-reduction
LCP	Light compensation point
ETRmax	maximum relative electron transport rate at saturating light
rETR	relative electron transport rate
α	the slope of the linear phase at sub-saturating light of the ETR vs. E curves
β	coefficient of downregulation/photoinhibition
Ek	the minimum saturating irradiance
RLC	Rapid Light Curve