DESIGN AND TESTING OF TWIG CHAMBERS FOR OZONE FUMIGATION AND GAS-EXCHANGE MEASUREMENTS IN MATURE TREES

A twig chamber system was developed for the exposure of mature trees t o ozone (O-3) under freld conditions. The fumigation system allowed th e exact control of O-3 concentrations in the chambers, the measurement of O-3 uptake as well as gas exchange measurements under ambient and controlled conditions during and after O-3 fumigation. Because of diff erences in individual twigs the system should provide the exposure of replicates to different O-3 treatments. Tests showed that temperature, humidity and O-3 concentrations inside the chambers were comparable w ith diurnal courses observed in the field. Comparative gas exchange me asurements indicated that there were no differences in net photosynthe sis and conductance of twigs outside the chambers and twigs which rema ined within the chambers for 23 weeks receiving ambient air.