Effect of Ozone on Photosynthesis, Vegetative Growth and Productivity of 'Prunussalicina' in the San Joaquin Valley of California. (Year 3)

摘要

In 1988, an experimental orchard of Cassleman plum (Prunus salicina) was plantedin open-top-fumigation chambers and exposed for 4 growing seasons to three ozone concentrations near Fresno, California. During the third year of the study, mean 12-h ozone levels (1991) were 0.034 ppm in the charcoal filtered chambers, 0.050 ppm in the ambient air chambers, 0.94 ppm in the ambient plus added ozone chambers and 0.058 ppm in the no-chamber field plots. Chronic ozone stress has a detrimental effect on photosynthesis, stomatal conductance, leaf appearance and retention, trunk growth, and yield. Yield was 19.8 kg per tree in the charcoal filtered chambers, 15.9 kg/tree in the ambient air chambers, 6.8 kg/tree in the ambient air plus ozone chambers and 15.8 kg/tree in the no-chamber plots. Premature leaf drop and a 35 percent yield loss occurred in 1990 at mean daily ozone concentrations greater than 0.09 ppm (the California Ambient Air Quality Standard). In 1991 the yield loss increased to 65%, indicating cumulative impact on long term productivity.