Abstract
Head lettuce ( Lactuca sativa L. cv ‘Empire’) was grown in the field and exposed in open-top chambers to proportional increments of ozone (O 3) from full charcoal filtration (CF) to twice ambient O 3 concentrations (NF × 2.0). Severe foliar injury developed on young plants exposed to O 3 concentrations 1.7 and 2.0 times greater than ambient (seasonal 7 hr means of 0.104 and 0.128 ppm, respectively). These exposure levels also reduced total head weight 13 and 35%, respectively, compared with CF plants. Marketable-sized head weight was reduced 21 and 80%, respectively. Plants in O 3-added chambers matured 2–3 weeks later than plants in low O 3 chambers. Regression analysis of yield data indicated that the threshold for significant yield reduction of head weight was > 0.083 ppm (seasonal 7-hr O 3 mean).
Published Version
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