Parameter | Formula | Definition |
---|---|---|
F, F′, Fs′ | n/a | Steady state fluorescence emission from dark- or light-adapted (‘) leaf, respectively. F′ is sometimes referred to as Fs′ when at steady state. |
Fm, Fm′ | n/a | Maximal chlorophyll fluorescence measured in a dark- or light-adapted state respectively |
F o , F o ′ | n/a | Minimal chlorophyll fluorescence measured in a dark- or light-adapted state respectively |
F v , F v ′ | n/a | Variable chlorophyll fluorescence measured as the difference between dark- or light-adapted Fm/Fm′ and Fo/Fo′. |
Fv/Fm | (Fm–Fo)/Fm | Maximum quantum efficiency of PSII. |
Fv′/Fm′ | (Fm′–Fo′)/Fm′ | Maximum efficiency of PSII in the light. |
Fq′/Fm′ | (Fm′–F′)/Fm′ | PSII operating efficiency: the quantum efficiency of PSII electron transport in the light. AKA ΦPSII, quantum yield or ΔF/Fm′ |
ETR or J | ΦPSII (AKA Fq′/Fm′) × PPFDa × (0.5) | Linear electron transport rate; where PPFDa is absorbed light (μmol m−2 s−1) and 0.5 is a factor that accounts for the partitioning of energy between PSII and PSI. |
NPQ | (Fm–Fm′)/Fm′ | Non-photochemical quenching: estimates the rate constant for heat loss from PSII. |
qL | (Fq′/Fv′)/(Fo′/F′) | Estimates the fraction of open PSII centers (QA oxidized); considered a more accurate indicator of the PSII redox state than qP |
qP | (Fm′–F′)/(Fm′–Fo′) AKA Fq′/Fv′ | Photochemical quenching: relates PSII maximum efficiency to operating efficiency. Non-linearly related to proportion of PSII centers that are open. 1–qP has also been used to denote proportion of closed centers |