Research Program Area: Ecosystem & Multimedia Effects
Nursery stock of plum (Prunus salicina Lindel., cv. Casselman) were planted 1 April 1988 in an experimental orchard at the University of California Kearney Agricultural Center near Fresno, California. The trees were enclosed in open-top fumigation chambers on 1 May 1989, and were exposed to three atmospheric ozone concentrations (charcoal filtered air, ambient air, and ambient air + ozone) from 8 May to 15 November 1989 and from 9 April to 9 November 1990. A no-chamber treatment plot was utilized to assess chamber effects on tree performance. The mean 12-h (0800-2000 h PDT) ozone partial pressures during the two-year experimental period in the charcoal filtered, ambient, ambient + ozone, and no chamber treatments were 0.044, 0.059, 0.111, and 0.064 ppm in 1989 and 0.038, 0.050, 0.090, and 0.050 ppm in 1990, respectively. Leaf net CO, assimilation rate of Casselman plum decreased with increasing atmospheric ozone concentration from the charcoal filtered to ambient t ozone treatment. There was no difference in plum leaf net CO, assimilation rate between the ambient chamber and no-chamber plots. Trees in the ambient t ozone treatment had greater leaf-fall earlier in the growing season than those of the other treatments. Cross-sectional area growth of plum decreased with increasing atmospheric ozone concentrations from the charcoal filtered to ambient t ozone treatment. Yield of plum trees in 1990 was 8.8, 6.3, 5.5, and 5.5 kg tree-1 in the charcoal filtered, ambient, ambient t ozone, and no-chamber treatments, respectively. Average fruit weight (g fruit-1) was not affected by atmospheric ozone concentrations. Fruit number per tree decreased as atmospheric ozone concentration increased from the charcoal filtered to ambient t ozone treatment. Decreases in leaf gas exchange and loss of leaf surface area were probable contributors to decreases in cross-sectional area growth and yield of young Casselman plum trees during orchard establishment.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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