Radiation interception and the growth of soyabeans exposed to ozone in open-top field chambers.
Soyabeans cv. Davis were grown in the field in open-top chambers ventilated with charcoal-filtered air, non-filtered air or non-filtered air to which 0.02, 0.04 or 0.06 p.p.m. ozone was added for 7 h/day. The interception of total solar radiation by the canopy was measured with tube solarimeters. Aboveground biomass and LAI were determined throughout the season. During vegetative growth, DM accumulation was linearly related to radiation interception for all treatments. The max. radiation interception attained decreased with increase in ozone conc., and earlier senescence gave shorter persistence of leaf cover. The seasonal mean value of the fraction of radiation intercepted decreased from 0.68 in filtered air to 0.65 in 0.06 p.p.m. ozone. The duration of seed growth decreased with increased O3, and the number of pods/plant and mean seed weight decreased, while the number of seeds/pod decreased only at the highest ozone conc. Seed yield at 0.06 p.p.m. ozone was about 50% lower than in filtered air. The lower light interception and shorter growth duration in ozone each accounted for <7% of the yield loss; it was concluded that the action of ozone resulted in lowered efficiency of DM production and altered seed and pod development which restricted yield.