An installation for measuring carbon dioxide and water vapour exchange rates with a precise environmental control

An open system has been designed which enables a simple and rapid manual regulation of the CO 2 concentration and absolute humidity in the assimilation chamber according to the actual CO 2 and water vapour exchange rates, respectively. This ensures a constant effective CO 2 concentration and humidity irrespective of the gas exchange of the leaves. The installation is supplemented with an irradiation system providing irradiance at the leaf level up to 3 200 μeinstein m −2 s −1 (400–700 nm), i. e. ca. 675 W m −2 .