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Chlorophyll fluorescence measurements

Carl Otto Ottosen: University of Aarhus

Chlorophyll fluorescence kinetics can be measured using any pulse modulated unit (Walz, Handy Pea ect).

  1. (dark adapted)

The Fv/Fm (dark adapted for >20 min using leaf clips) should be measured at least on the beginning of the day on 30 minutes dark adapted leaves. Data from 3-6 leaves per genotype should be sufficient.  Use the first fully developed leaf for the measurements.

  1. (no dark adaptation)

The Fʹq/Fʹm values for the leaves in light can measured with the help of a leaf clip holder using an external stabilized light source can used as the actinic light source. The middle portion of the leaf is used and the measuring light should be so low that it does not drive photosynthesis (0.15 µmol m-2s-1). After few seconds, a 0.6-8[1] s saturation flash of white light (approximately 6000 µmol m-2s-1) should be applied to determine the maximal fluorescence (Fʹm). Then the actinic light (light level close to the normal average light level) was turned on and continued until steady state of fluorescence (Fʹ) condition was attained. The measurement can be repeated with at least 30 min interval depending on species and time of year. A monipam (Walz) can be used to make the measurement too.

An option is also to make rapid light response curves (possible with most PAM’s. The standard is 10 steps up to 1200 with 30 sec interval. Be aware that the RLP’s can be tricky as the battery does not always deliver enough power for the high light flashes.