open system for plant gas-exchange analysis

An open system was designed for studies of photosynthesis and transpiration on single leaves of crop plants. The system contained several features that facilitated the measurement of gaseous exchange between leaves and their environment. An inexpensive unit, requiring little attention, was developed to control the humidity of the influx air. Also, a system of solenoid valves was arranged to control the sequence of sample analysis. This allowed several cuvettes to be monitored sequentially in a short period of time. The valve system was designed to minimize lag time to obtain stable readings following valve activation. A 2-min sampling period was used for each cuvette. A dew-point hygrometer was used to measure water vapor content of the air. The dew-point hygrometer, designed for unattended outdoor use, was modified for cuvetting studies. The performance of the system is described and evaluated.