Research Program Area: Ecosystem & Multimedia Effects
Two varieties of processing tomatoes, UC-204-B and E-6203 were exposed to four levels of ozone and two levels of SO2 in plastic covered open top chambers at Parlier, California. Ozone concentrations were based on ambient levels in the area and were .25, .50, 0.90 and 1.5 times ambient levels. Six hours per day, four days per week a SO2 concentration of 0.1 ppm was maintained in the SO2-added experiments by metering in anhydrous SO2 gas from a cylinder. Treatments were maintained from June 10 until August 26 when the chambers were removed to facilitate fruit harvest.
The entire tomato vine with fruit attached was cut off at ground level prior to picking off all of the fruit. Upon removal the fruit was sorted into three categories: "reds", "greens", and "rots", which were weighed separately. One preweighed bin containing approximately 25 kg of ripe (red) fruit was counted to determine mean fruit weight as an indication of mean fruit size. Ten pound subsamples of ripe fruit representing each variety from each subplot were obtained and delivered to the U.C., Davis Tomato Quality Laboratory for standard quality tests.
Results of yield measurements indicated a 20% reduction in vine weights and 27% reduction in weight of good red fruit by vines receiving ambient ozone as compared with similar vines receiving filtered air. Exposure to SO2 reduced vine growth approximately 7% and red fruit production approximately 8% as compared with no SO2 exposure. Increasing the ozone level to 1.5 times ambient reduced yields an additional 15% but did not reduce vine weights, an indication the high ozone may be affecting flower production and / or pollination.
Fruit quality data from the Tomato Quality Laboratory indicated that soluble solids (Brix) and viscosity were reduced as ozone levels increased. Exposure to 0.1 ppm SO2 tended to increase solids somewhat but had no significant effect on other quality criteria.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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