A gas-exchange system for measuring the productivity of plant populations in controlled environments

Abstract

An open gas-exchange system that will continuously measure the CO2 exchange of a small population of plants is described. The plant chamber was a controlled environment cabinet; air supply to the cabinet was measured by a venturi and differential pressure transducer and the CO2 differential between entering and exiting air was measured with an infrared gas analyzer. Carbon dioxide gain or loss by the population of plants was calculated from the CO2 differential and the air flow to the cabinet. The accuracy of the CO2 monitoring system was determined by comparing the carbon gain calculated from the CO2 measurements to the carbon gain determined by a harvest procedure. In four experiments, the gas-exchange system measured 85–99% of the actual carbon gain by the plants. Since the gas-exchange system provides a measure of absolute rather than relative productivity it is useful for examining the effect of various treatments on plant productivity.