© 1996 Heron Publishing—Victoria, Canada
Carbon partitioning and allocation in northern red oak seedlings and mature trees in response to ozone
L. J. Samuelson (1) and J. M. Kelly (2)
1. School of Forestry, M. White Smith Hall, Auburn University, AL 36849-5418, USA / 2. Department of Forestry, Iowa State University, Ames, Iowa 50011-1021, USA / Received September 20, 1995
Summary
Northern red oak (Quercus rubra L.) seedlings and trees differ in their response to ozone. Previous work reported reductions in net photosynthesis, carboxylation
efficiency and quantum yield of mature tree leaves, whereas seedling processes were unaffected by the same ozone exposure.
To further characterize differences in ozone response between seedlings and mature trees, we examined carbon partitioning
and allocation in 32-year-old trees and 4-year-old seedlings of northern red oak after exposure to subambient (seasonal SUM00
dose (sum of all hourly ozone exposures) = 31 ppm-h), ambient (SUM00 dose = 85 ppm-h) and twice ambient (SUM00 dose = 151
ppm-h) ozone concentrations for three growing seasons. For mature trees, ozone exposure decreased foliar starch partitioning,
increased starch partitioning in branches and increased 14C retention in leaves. In contrast, starch partitioning in leaves and branches, and foliar 14C retention in seedlings were unaffected by ozone exposure, but soluble carbohydrate concentrations in coarse and fine roots
of seedlings were reduced. Differences in carbohydrate demand between seedlings and mature trees may underlie the higher leaf
ozone uptake rates and greater physiological response to ozone in mature northern red oak trees compared with seedlings.
Keywords:
Quercus rubra, carbon metabolism, scaling.
