skip to main content

Title: Leaf gas exchange along a light graident in a sugar maple forest canopy experimentally exposed to ozone pollution

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.
Authors:
; ; ;  [1]
  1. (Univ. of Minnesota, St. Paul (United States))
Publication Date:
OSTI Identifier:
6143414
Report Number(s):
CONF-930798--
Journal ID: ISSN 0012-9623; CODEN: BECLAG
Resource Type:
Conference
Resource Relation:
Journal Name: Bulletin of the Ecological Society of America; (United States); Journal Volume: 74:2; Conference: 78. annual Ecological Society of America (ESA) meeting, Madison, WI (United States), 31 Jul - 4 Aug 1993
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; 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