An Open-Circuit Infrared Gas Analysis System for Measuring Aquatic Plant Photosynthesis at Physiological pH

Abstract

A temperature-controlled assimilation chamber and gas circuit are described which allow steady-state measurement of photosynthesis by aquatic plants in media containing bicarbonate ions. Gas entering the assimilation chamber is divided into fine bubbles by passage through a sintered glass disc which forms the chamber floor. Rapid achievement and subsequent maintenance of chemical and phase equilibria are ensured by sustaining a high gas flow through the chamber via a recirculating loop in the gas circuit. Incorporation of this unit in a conventional open infrared gas analysis system allowed accurate and sensitive measurements to be made over wide ranges of pH and CO₂ concentration.