Photochemical oxidants potentiate yield losses in snap beans attributable to sulfur dioxide.

Field-grown snap beans (Phaseolus vulgaris) were given recurring midday exposures to sulfur dioxide in open-top field chambers containing ambient photochemical oxidants. There was a linear correlation (correlation coefficient = -.99) between increasing concentrations of sulfur dioxide and the yields of snap beans. Synergism was indicated for the mixtures of ambient ozone plus sulfur dioxide, leading to threefold greater yield losses in nonfiltered air than in charcoal-filtered air (to remove the ozone). Even the lowest sulfur dioxide dose in nonfiltered air reduced the yields of Astro, a cultivar that exhibited no visible pollutant-induced foliar injury.