Ozone-exposure responses of black cherry and red maple seedlings

Abstract

Field foliar injury surveys have been used to identify ozone injury in deciduous tree species growing in forested areas in the southeastern United States. Whether ozone-induced foliar symptoms are indicative of leaf photosynthetic and growth reductions is not well understood. This research tested the hypothesis that ozone-induced foliar injury is accompanied by reductions in leaf gas exchange and growth in 1-year-old black cherry ( Prunus serotina Ehrh.) and red maple ( Acer rubrum L.). Seedlings were grown under a 75% reduction of ambient light and fumigated with sub-ambient, ambient or twice-ambient concentrations of ozone on a 24-hr basis for one growing season (5 months). For both species, only leaves exposed to the twice-ambient ozone treatment displayed visible symptoms. Net photosynthesis and leaf conductance of red maple and black cherry leaves declined, and internal CO 2 concentrations increased in response to ozone treatment. Ozone reduced the height growth and the root/shoot ratio of black cherry, but ozone did not influence red maple growth. These results indicate that ozone-induced foliar injury may be accompanied by reductions in leaf gas exchange in black cherry and red maple, and by growth reductions in black cherry.