Apparatus for the Simultaneous Measurement of Water Vapour and Carbon Dioxide Exchanges of Single Leaves

Abstract

Equipment is described which delivers air with concentrations of CO₂ and water vapour closely controlled in the ranges 0 to 2500 ppm and 5 to 15 mb respectively, at flow rates of up to 10 1 min^-1, to each four leaf chambers. The leaf temperature is controlled to ±0.5 °C and, with a light intensity of 0.3 cal cm^-2 min^-1 visible radiation (0.4 to 0.7 μm) leaf temperature can be maintained at 17.5 °C.The apparatus used to measure the concentration differences between the water vapour and CO₂ entering and leaving the leaf chamber (used to calculate transpiration, photosynthetic, and respiration rates) is described in detail.Results of tests, which show the necessity for mounting a fan within the leaf chamber, are reported.Typical light- and CO₂-response curves are given for kale leaves (Brassica oleracca var. acephala) and an attempt is made to quantify the errors in the measurement of photosynthesis and transpiration.