Leaf gas exchange along a light graident in a sugar maple forest canopy experimentally exposed to ozone pollution
- Univ. of Minnesota, St. Paul (United States)
The impact of ozone on leaf gas exchange in a forest canopy as influenced by light environment was studied in a 35-year-old stand of sugar maple (Acer sacchharum) in southern Wisconsin. We developed a chamberless system to expose branches to elevated concentrations of ozone. Ten branches and ten paired controls in the upper canopy (14 to 16 m) were selected along a light gradient, ranging from sunlit (14.5 mol m[sup [minus]2] day[sup [minus]1] PPFD) to deeply shaded (0.6 mol m[sup [minus]2] day[sup [minus]1] PPFD). The branches were exposed for 8 hours each day to ozone concentrations averaging 95 nl 1[sup [minus]1](+/-13 SD), about twice the ambient levels between June and September. Among the branches, area-based rates of light-saturated photosynthesis and dark respiration were positively correlated with mean daily integrated PPFD. Light-saturated rates of photosynthesis and chlorophyll concentrations declined while dark respiration increased with increasing ozone dose. Over time stomatal conductance became uncoupled from light-saturated photosynthesis rates in exposed branches. Photosynthesis and quantum yield were reduced more in a shaded branch than in a sunlit branch in response to ozone treatment. In general, shaded branches were more sensitive to ozone than sunlit branches.
- OSTI ID:
- 6143414
- Report Number(s):
- CONF-930798-; CODEN: BECLAG
- Journal Information:
- Bulletin of the Ecological Society of America; (United States), Vol. 74:2; Conference: 78. annual Ecological Society of America (ESA) meeting, Madison, WI (United States), 31 Jul - 4 Aug 1993; ISSN 0012-9623
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
LEAVES
PHOTOSYNTHESIS
OZONE
BIOLOGICAL EFFECTS
VISIBLE RADIATION
VARIATIONS
AIR POLLUTION
CHLOROPHYLL
FORESTS
MAPLES
RESPIRATION
WISCONSIN
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DEVELOPED COUNTRIES
ELECTROMAGNETIC RADIATION
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MAGNOLIOPHYTA
MAGNOLIOPSIDA
NORTH AMERICA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHYTOCHROMES
PIGMENTS
PLANTS
POLLUTION
PORPHYRINS
PROTEINS
RADIATIONS
SYNTHESIS
TREES
USA
560300* - Chemicals Metabolism & Toxicology