Single-turnover flashes to saturate the Q(A) reduction in a leaf were generated by the light-emitting diodes from a double modulation kinetic chlorophyll fluorometer

The earlier developed double-modulation chlorophyll (Chl) fluorometer was m odified for measurements with intact leaves of higher plants. The Chi fluor ometer is based on a non-periodic modulation of both actinic and measuring flashes, In addition, continuous orange actinic and far-red radiation were produced by separate arrays of light-emitting diodes (LEDs). Programmable t iming of the flashes allows to cover a wide dynamic range from microseconds to minutes. We have demonstrated thar the LEDs can produce single-turnover flashes that saturate QA reduction of intact leaves of Glyceria maxima and shoots of Picea abies.