Simultaneous Measurement of Oxygen, Carbon Dioxide, and Water Vapour Exchange in Intact Plants

Abstract

A low flow of air is passed through a temperature-controlled plant chamber in order to obtain relatively large (∼300–500 μl-1) differences in [O₂] between influx and efflux streams. These differences are measured with a stabilized O₂ electrode system incorporating elements of gas conditioning electronic zero suppression and signal amplification. Changes in [O₂] of 400 μl l-1 can be detected at full scale recorder deflection against a background concentration of 21% O₂. The concentrations of CO₂ and H₂O within the chamber are held constant by con-trolled-flow CO₂-scrubbing and dehumidifying loops. Carbon dioxide, H₂O, and O₂ fluxes are measured and leaf diffusion resistance and internal [CO₂] are calculated in essentially ‘real time’.