A new type of climatized gas exchange chamber for net photosynthesis and transpiration measurements in the field.

A temperature- and humidity-controlled plant chamber for CO and HO exchange measurements in the field is described in which the heat exchanger assembly and humidity controlling water vapour trap are separated from the plant cuvette. The shape and construction material of the plant cuvette can vary according to the demands of the experimental conditions and the size and growth form of the plant. The natural illumination field is only slightly altered in this plant cuvette. In the chamber, the temperature and humidity conditions can either be held constant throughout a wide range of conditions or can be programmed to track ambient condition. In this manner, not only temperature and absolute humidity are replicated, but it is also possible to reproduce the natural conditions of water vapour gradient between the evaporating surfaces in the mesophyll and the atmosphere, the relative humidity of the air, and the temperature difference between the leaf and the ambient air. Thus, the chamber appears to be an appropriate instrument to investigate with sufficient accuracy the reactions of individual plants in cultivation or in natural communities under field conditions.