On the use of a field exposure system to estimate air pollution levels

The paper describes a field exposure system involving the application of growing chambers, ventilated with filtered or nonfiltered ambient air. The diffusive resistance of primary leaves of beans (Phaseolus vulgaris L.), growing in medium with ammonium or nitrate as nitrogen source, has been used as indicator for low level air pollution, which does not produce visible leaf injury. In severely polluted atmosphere an addition of sodium chloride affected inversely the degree of injury.