An Apparatus to Produce Gas Mixtures with Controlled CO2, O2, and Water Vapor Concentrations

An apparatus to produce continuous gas mixtures for use in measurements of plant gas exchange is described. A wide range of CO 2 and water vapor concentrations can be provided and O 2 concentration can be varied from 0 to 21%. Changes in the concentrations of the components are accomplished conveniently, rapidly, and independently. With occasional adjustments, CO 2 and O 2 concentrations can be maintained to within ± 1 μl/l and ± 0.1%, respectively. Dew point of the gas mixture can be maintained to within ± 0.05 C.