1. Background
  2. Data Collection Methods
  3. Data Quality Control
  4. Summary

Key Concepts for Measurement

Light Doubling Technique

(as described in Maxwell and Johnson, 2000)

This technique uses a high intensity, short duration flash of light (SP) to temporarily close all PSII reaction centers. As a result, photochemical quenching is temporarily reduced to zero.

Variables Measured Directly

  1. F0 - yield of fluorescence in the absence of photosynthetic light
  2. F0' - light-adapted zero-level fluorescence obtained after turning off photosynthetic light
  3. Fm0 - maximum fluorescence; obtained in the absence of photochemical quenching
  4. Fm' - light-adapted maximum fluorescence; obtained after a saturating pulse of light
  5. Ft - fluorescence at a given time, usually at steady-state just before a saturating pulse of light.