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

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Abstract
Measurements of rapid changes in concentrations and fluxes of gaseous compounds relating to photosynthetic gas exchange are commonly performed using flow‐through cuvettes in connection with infrared gas analysers. The accuracy and repeatability of these measurements relies ultimately upon the design of the system as a whole, rather than upon each of its components, and therefore the calibration and testing of the system should be performed keeping this in mind. We present here a simple and efficient method for the calibration of such a measurement system using a precisely determined CO2 flow. This method gives us the opportunity to take into account any disturbing effects caused by undesired properties of the chamber or tubing materials. With the proposed calibration method, the accuracy of the CO2 flux measurement is improved from 8% up to the level of 2%, determined mainly by the accuracy of the control gas used for calibration of the CO2 analyser.