Impacts of ozone on photosynthesis and conductance of tree versus seeling Quercus Rubra L. Foliage

Conference · Sat May 01 04:00:00 EDT 1993 · Plant Physiology; (United States)

OSTI ID:6280109

Hanson, P J; Wullschleger, S D ^[1]; Samuelson, L J; Edwards, G S ^[2]

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1. Oak Ridge National Lab., TN (United States)
2. Tennessee Valley Authority, Norris (United States)

Extrapolation of ozone impacts on seedlings to large trees and forest stands is a common objective of recent assessment activities. This study utilized a replicated open-top chamber facility to test the effect of subambient, ambient, and twice ambient ozone on light-saturated net photosynthesis (Pn) and leaf conductance (gs) of leaves from mature trees and genetically-related seedlings. Intensive gas exchange measurements were collected four times during the 1992 growing season. At leaf maturity (mid-June) Pn and gs of the mature tree foliage were 60-80% greater than for seedling leaves, but there were no differences in leaf water status. At the end of the growing season, the mature tree foliage showed reduced Pn and gs with increasing levels of ozone exposure, but the seedling leaves remained unaffected. Calculated internal ozone uptake by seedling foliage was less than for mature tree leaves because the seedling foliage had lower gs throughout the growing season. Plots of normalized Pn data over time (relative to the subambient treatment) revealed a threshold for ozone effect for the mature tree leaves at a cumulative internal uptake of [approx]20 mmol O[sub 3] M[sup [minus]2] of leaf area. Ozone uptake by seedling foliage was below this threshold. These data suggest that seedling exposure studies may underestimate responses of mature trees in the field.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6280109
• Report Number(s): CONF-9307119--
• Conference Information: Journal Name: Plant Physiology; (United States) Journal Volume: 102:1
• Country of Publication: United States
• Language: English

Related Subjects

560300* -- Chemicals Metabolism & Toxicology
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BIOLOGICAL EFFECTS
CHEMICAL REACTIONS
HYDROGEN COMPOUNDS
LEAVES
MAGNOLIOPHYTA
MAGNOLIOPSIDA
OAKS
OXYGEN COMPOUNDS
OZONE
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PLANTS
SEEDLINGS
SYNTHESIS
TREES
WATER