Variation in photosynthesis and stomatal conductance in an ozone-stressed Ponderosa pine stand: light response

Journal Article · Tue Jun 01 04:00:00 EDT 1982 · For. Sci.; (United States)

OSTI ID:5689435

Cooyne, P I ^[1]; Bingham, G E

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1. USDA-ARS, Woodward, OK

The seasonal course (May to October 1977) of gross photosynthesis (from /sup 14/CO/sub 2/ uptake and stomatal conductance) in a stand of ponderosa pine (Pinus ponderosa Laws.) in the San Bernardino National Forest was characterized as a function of light. Nine sapling trees, classified for comparative studies into three chronic injury classes (slight, moderate, severe) had experienced oxidant fumigations from California's South Coast Air Basin for approximately 18 years, since their establishment following fire. The CO/sub 2/-transfer pathway was partitioned into its stomatal and residual (mesophyll, carboxylation, excitation) resistance components, for conditions of light saturation and 20/sup 0/C. Light-saturated gross photosynthetic rates and photochemical conversion efficiencies were highest in the current-year needles and decreased with increasing needle age and oxidant injury. Maximum stomatal conductance and stomatal sensitivity to increasing light during stomatal opening followed a trend similar to that of photosynthesis, except for current-year needles, where conductance parameters were highest in the severely injured trees. This higher conductance may contribute to observed differential ozone sensitivity in ponderosa pine. Premature senesence and abscission of the 1-year (severely injured trees) and 2-year (slight to moderate injury) needles occurred at about the time CO/sub 2/ uptake dropped to 10 percent of the potential for current needles of slightly injured trees without foliar injury symptoms. The ratio of the stomatal CO/sub 2/ resistance to the total CO/sub 2/ resistance decreased with increasing oxidant injury and needle age, suggesting that loss of photosynthetic capacity was primarily related to the loss of chloroplast function rather than to increased resistance of CO/sub 2/ diffusion through the stomata.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5689435
• Journal Information: For. Sci.; (United States), Journal Name: For. Sci.; (United States) Vol. 28:2; ISSN FOSCA
• Country of Publication: United States
• Language: English

Related Subjects

500100* -- Environment
Atmospheric-- Basic Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
AIR POLLUTION
BIOLOGICAL EFFECTS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CELL CONSTITUENTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHLOROPLASTS
CONIFERS
DIFFUSION
ELECTROMAGNETIC RADIATION
LEAVES
OPENINGS
OXIDES
OXYGEN COMPOUNDS
OZONE
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PHYSIOLOGY
PINES
PLANTS
POLLUTION
RADIATIONS
STOMATA
SYNTHESIS
TREES
VISIBLE RADIATION