A portable system for measuring carbon dioxide and water vapour exchange of leaves

Abstract. The apparatus described here is a fully portable, steady-state gas exchange system for simultaneous measurements of the CO2 exchange and transpiration of single, attached leaves. The leaf cuvette provides temperature, humidity, and CO2-concentration control. The system is suitable for either surveys or detailed studies of photosynthetic and stomatal responses to environmental variables. Representative data demonstrate the response time characteristics of the system and constitute the first field evidence of stomatal behaviour consistent with a recent hypothesis concerning the optimum pattern of stomatal conductance for the maximization of water-use-efficiency.