Project at a Glance

Title: Effect of ozone on photosynthesis vegetative growth and productivity of prunus salicina in the San Joaquin Valley of California: Final report contract no. A033-128 (year three)

Principal Investigator / Author(s): Williams, Larry Edwards

Contractor: University of California, Davis

Contract Number: A033-128

Research Program Area: Ecosystem & Multimedia Effects, Atmospheric Processes

Topic Areas: Agriculture, Ecosystem Impacts, Field Studies, Impacts


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, from 9 April to 9 November 1990, and from 1 April to 31 October 1991. This report will detail the results of the 1991 growing season. A no-chamber treatment plot was utilized to assess chamber effects on tree performance. The mean 12-h (0800-2000 h PDT) ozone concentration during the 1991 experimental period in the charcoal filtered. ambient, ambient + ozone, and no- chamber treatments were 0.034, 0.050, 0.094 and 0.058 ppm, respectively. Leaf net CO2 assimilation rate of Casselman plum decreased with increasing atmospheric ozone concentration from the charcoal filtered to ambient + ozone treatment. There was no difference in plum leaf net CO2 assimilation rate between the ambient chamber and no-chamber plots. Trees in the ambient + ozone treatment had greater leaf-fall earlier in the growing season than those of the other treatments. Yield of plum trees in 1991 was 19.8, 15.9,6.8 and 15.8 kg tree-1 in the charcoal filtered. ambient, ambient + ozone, and no-chamber treatments, respectively. Average fruit weight (g fruit-1) was not affected by atmospheric ozone concentration. Fruit number per tree decreased as atmospheric ozone concentration increased from the charcoal filtered to ambient + ozone treatment. Decreases in leaf gas exchange and loss of leaf surface area were probable contributors to decreases in yield of Casselman plum trees in a commercial bearing orchard.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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