An inexpensive system for exposing plants in the field to elevated concentrations of CO₂

An inexpensive, potentially mobile field exposure system is described which may be easily constructed by a small workshop. It may be operated as an open‐top with a frustrum or covered with a polycarbonate ‘lid’. The system is cost‐effective for CO 2 exposure work because the small size allows provision of CO 2 ‐enriched atmospheres over prolonged periods at relatively low cost. A preliminary assessment of the chambers has been made and concentrations can be maintained at ±6% for a target atmosphere of 680 cm 3 m −3 CO 2 under normal operating conditions. Other chamber environmental conditions are reported.