© 1996 Heron Publishing—Victoria, Canada
Light environment alters ozone uptake per net photosynthetic rate in black cherry trees
T. S. Fredericksen (1, 2), T. E. Kolb (3), J. M. Skelly (4), K. C. Steiner (5), B. J. Joyce (5) and J. E. Savage (4)
1. Environmental Resources Research Institute, Pennsylvania State University, University Park, PA 16802, USA / 2. National Audubon Society, 204 Ferguson Building, University Park, PA 16802, USA / 3. School of Forestry, Northern Arizona University, P.O. Box 15018, Flagstaff, AZ 86011-5018, USA / 4. Department of Plant Pathology, Pennsylvania State University, University Park, PA 16802, USA / 5. School of Forest Resources, Pennsylvania State University, University Park, PA 16802, USA / Received date not available
Summary
Foliar ozone uptake rates of different-sized black cherry (Prunus serotina Ehrh.) trees were compared within a deciduous forest and adjacent openings in north-central Pennsylvania during one growing
season. Study trees included open-grown seedlings and saplings, forest understory seedlings and saplings, and sunlit and shaded
portions of mature canopy tree crowns. Instantaneous ozone uptake rates were highest in high-light environments primarily
because of higher stomatal conductances. Low ozone uptake rates of seedlings and saplings in the forest understory could be
attributed partially to lower average ambient ozone concentrations compared to the canopy and open environments. Among the
tree size and light combinations tested, ozone uptake rates were highest in open-grown seedlings and lowest in forest-grown
seedlings. Despite lower ozone uptake rates of foliage in shaded environments, ozone uptake per net photosynthesis of foliage
in shaded environments was significantly higher than that of foliage in sunlit environments because of weaker coupling between
net photosynthesis and stomatal conductance in shaded environments. The potential for greater ozone injury in shaded environments
as a result of greater ozone uptake per net photosynthesis is consistent with previous reports of greater ozone injury in
shaded foliage than in sunlit foliage.
Keywords:
air pollution, irradiance, Prunus serotina, shade, stomatal conductance.
