Chlorophyll Fluorescence Calculator

Enter the raw fluorescence values measured with your PAM fluorometer to derive Fv/Fm, ΦPSII, NPQ, qP, qL, qN, and ETR — with a healthy/stress interpretation. These parameters are measured, not estimated from a light recipe, PPFD, or spectrum.

Compatible inputs from: Walz PAM-2500 / MINI-PAM · LI-COR LI-600 · Apogee MFC · PhotosynQ MultispeQ

Measurements

F₀ — minimal fluorescence (dark-adapted)Weak measuring beam after 15–30 min dark adaptation.Fm — maximal fluorescence (dark-adapted)During a saturating pulse (~3000–8000 µmol m⁻² s⁻¹).

Assumptions (for ETR)

Leaf absorptanceDefault 0.84.Fraction to PSIIDefault 0.5.

Using defaults → ETR is reported as relative ETR (rETR). Supply a measured leaf absorptance for an absolute ETR.

Results

Enter F₀ and Fm to compute Fv/Fm.

Healthy dark-adapted Fv/Fm for unstressed C3 leaves is ~0.78–0.84 (optimum ≈ 0.83); below ~0.70 indicates photoinhibition. The optimum is species- and condition-dependent (dark-adaptation time, leaf temperature, measuring-beam and saturation-pulse settings, leaf age). Treat the interpretation as advisory, not a species-calibrated threshold.

Equations: Maxwell & Johnson (2000); Genty et al. (1989); Baker (2008); Oxborough & Baker (1997); Björkman & Demmig (1987); Jassby & Platt (1976).

Measurement log0 saved

No saved readings yet. Compute a value above, then “Save reading” to build a time series (stored in your browser; export anytime as CSV).

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