CHRONIC OZONE OR SULFUR DIOXIDE EXPOSURES, OR BOTH, AFFECT THE EARLY VEGETATIVE GROWTH OF SOYBEAN

Abstract

Soybean (Glycine max (L.) Merr.) cult Hood and Dare were exposed to low concentrations of ozone or sulfur dioxide, or both, during the first 3 wk of growth. Foliar injury occurred on both cultivars in the ozone and mix treatments. Dare developed more foliar injury than Hood. Plant height, top and root fresh and dry weights, and the dry shoot–root ratios were significantly reduced by the 10-pphm ozone treatment. The mix of 5 pphm ozone plus 5 pphm sulfur dioxide significantly reduced top fresh weight, root fresh and dry weights, and shoot–root ratios. Treatments of 5 pphm ozone, 5 pphm or 20 pphm sulfur dioxide had no significant effects on plant growth. The growth reductions resulting from the ozone–sulfur dioxide mix were greater than the additive reductions of the single gases. The lack of a significant cultivar × treatment interaction indicated that the growth of the two cultivars responded similarly to the various treatments.