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

Journal Article · Tue Jun 01 00:00:00 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), Vol. 28:2
• Country of Publication: United States
• Language: English

Related Subjects

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