A large-scale fumigation system for investigating interactions between air pollution and cold stress on plants.

A new large-scale closed chamber fumigation system with cooling facilities is described for studying effects of low concentrations of SO(2), NO(2) and O(3) and low temperatures on woody species and herbaceous plants. The system is based on modified hemispherical greenhouses with a forced air ventilation system. This provides a chamber environment with low spatial variability of pollutant gas concentrations and rapid air circulation which allows exposure of plants at near ambient temperatures and relative humidity. Large capacity cooling units come into operation when ambient temperatures fall below 0 degrees C, and these allow chamber temperatures to be lowered by an additional 4 to 8 degrees C in experiments designed to test whether exposure to pollutants enhances the frost sensitivity of plants.