USE OF A FIELD RELEASE SYSTEM TO DISTINGUISH THE EFFECTS OF DOSE AND CONCENTRATION OF SULFUR-DIOXIDE ON WINTER BARLEY

A field release system was used to study the responses of winter barley (Hordeum vulgare cv. 'Igri') to intermittent sulphur dioxide (SO2) exposure. Separate plots were exposed for 1 day to 188 nl l-1, 3 days to 63 nl l-1 or 6 days to 29 nl l-1 within a 6-day cycle that was repeated 24 times throughout the growing season. There were no responses to SO2 of shoot dry weight, leaf area or grain yield, even to the rather severe exposure given by the highest concentration. In contrast, responses had been obtained by all the above parameters from previous continuous exposures of the same barley cultivar to SO2 concentrations in this range. We conclude that, for this cereal and pollutant combination, responses were determined by dose or average concentration, not by intermittent concentration peaks.