Project at a Glance

Title: Effects of ozone on photosynthesis , vegetative growth and development of woody perennials in the San Joaquin Valley of California

Principal Investigator / Author(s): Williams, L E

Contractor: University of California, Davis

Contract Number: A733-126

Research Program Area: Ecosystem & Multimedia Effects

Topic Areas: Ecosystem Impacts


Nursery stock of nine fruit and nut tree species were planted in open-top chambers on 1 April 1988 at the University of California's Kearney Agricultural Center located in the San Joaquin Valley. The trees were then exposed to three levels of atmospheric ozone partial pressures (charcoal filtered air, ambient air, or ambient air t ozone) from 1 August to 17 November 1988. The mean 12-h (0800-2000 h) ozone partial pressure measured in open-top chambers of the charcoal filtered treatment averaged 0.030 ÁPa Pa-1 (0.030 ppm) ozone during the experimental period. Mean ozone partial pressures measured in the ambient chambers were 0.051 ÁPa Pa-1 (0.051 ppm) and those in the ambient t ozone treatment 0.117 ÁPa Pa-1 (0.117 ppm) over the same time period. The relationship between leaf net CO, assimilation rate and 12-h mean ozone partial pressure decreased linearly with increasing ozone partial pressure for the almond, plum, apricot, prune, pear, and apple cultivars. Stomatal conductances (g,) of apricot, prune, apple, almond, and plum also decreased linearly with increasing ozone partial pressure. Cross-sectional area relative growth rates (RGRs) of almond, plum, apricot, pear, and apple declined linearly with increasing ozone partial pressure. Net CO, assimilation rate, stomatal conductance, and trunk growth of cherry, peach, and nectarine were unaffected by the ozone treatments. The results indicate that decreases in leaf gas exchange were probable contributors to decreases in young tree growth of the susceptible species/cultivars. However, several commercial fruit tree species/cultivars were identified as being relatively tolerant to ozone based upon measurements taken in this study.

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

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