Injury, Stomatal Conductance, and Abscisic Acid Levels of Pea Plants following Ozone plus Sulfur Dioxide Exposures at Different Times of the Day.

Pea (Pisum sativum L. cv Alsweet) plants were exposed to mixtures of ozone plus sulfur dioxide at different times of the day. Injury, evaluated either as necrosis or chlorophyll, was greatest at midday when stomatal conductance was greatest. Abscisic acid levels were similar over the day, and showed no relation to stomatal conductance.