Variation in photosynthesis and stomatal conductance in an ozone-stressed ponderosa pine stand: light response
- Southern Plains Range Research Station, 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% of the potential for current needles of slightly injured trees without foliar injury symptoms. The ratio of 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:
- 5983955
- Journal Information:
- For. Sci.; (United States), Journal Name: For. Sci.; (United States) Vol. 28:2; ISSN FOSCA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Comparative ozone dose response of gas exchange in a ponderosa pine stand exposed to long-term fumigations
Ozone dosage response of ponderosa pine seedlings
Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BIOLOGICAL EFFECTS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CONIFERS
DATA
ELECTROMAGNETIC RADIATION
EXPERIMENTAL DATA
INFORMATION
LEAVES
NUMERICAL DATA
OPENINGS
OXIDES
OXYGEN COMPOUNDS
OZONE
PHOTOCHEMICAL REACTIONS
PHOTOSENSITIVITY
PHOTOSYNTHESIS
PINES
PLANTS
RADIATIONS
SEASONAL VARIATIONS
SENSITIVITY
STOMATA
SYNTHESIS
TRANSPIRATION
TREES
VARIATIONS
VISIBLE RADIATION
WEIGHT