An improvement of the method for calibrating measurements of photosynthetic CO2 flux

Measurements of rapid changes in concentrations and fluxes of gaseous compo unds relating to photosynthetic gas exchange are commonly performed using f low-through cuvettes in connection,vith infrared gas analysers. The accurac y and repeatability of these measurements relies ultimately upon the design of the system as a whole, rather than upon each of its components, and the refore the calibration and testing of the system should be performed keepin g this in mind. We present here a simple and efficient method for the calib ration of such a measurement system using a precisely determined CO2 flow. This method gives us the opportunity to take into account any disturbing ef fects caused by undesired properties of the chamber or tubing materials, Wi th the proposed calibration method, the accuracy of the CO2 flux measuremen t is improved from 8% up to the level of 2%, determined mainly by the accur acy of the control gas used for calibration of the CO2 analyser.