Quantifying short term O3 exposure effects on the level of nighttime transpiration. (Contributo in atti di convegno)

Type
Label
  • Quantifying short term O3 exposure effects on the level of nighttime transpiration. (Contributo in atti di convegno) (literal)
Anno
  • 2006-01-01T00:00:00+01:00 (literal)
Alternative label
  • Grulke N.E., Paoletti E. (2006)
    Quantifying short term O3 exposure effects on the level of nighttime transpiration.
    in Impacts of Air Pollution and Climate Change on Forest Ecosystems, Riverside, California
    (literal)
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  • Grulke N.E., Paoletti E. (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#descrizioneSinteticaDelProdotto
  • A novel gas exchange system that concurrently supplies known O3 concentrations, and measures H2O, O3, and CO2 flux (“HOC” system) to leaves was used to assess short term O3 exposure effects on the level of nighttime transpiration. Two experiments were conducted. In the first, we tested the effect of short term acute O3 exposure on nighttime transpiration in California black oak (deciduous, Quercus kellogii) and blue oak (evergreen, Quercus douglasii) exposed previously to either charcoal-filtered air, or chronically elevated O3 for 8 h per day (70 ppb) in open-top chambers. Both chronic (70 ppb daily for 1 and 2 months, respectively) and acute (~180 ppb, 1 h) effects were tested for simple additive or synergistic effects. In the second experiment, we tested for the effect of a range of short term O3 exposures, to determine whether there was an inciting O3 concentration above which significant nighttime transpiration was induced (“threshold” effect), and how long significant nighttime transpiration persisted (“memory” effect). A range in O3 concentrations from 0 to 180 ppb for 1 h was used to elicit responses. In both the first and second experiments, individual leaves were exposed to either O3-free air (using a commercially available gas exchange system), or elevated O3 concentrations (using the HOC system) for one hour. During the night after the daytime exposure, stomatal conductance was measured on both the unexposed and exposed leaves. In order to test for “memory” effects, stomatal conductance was measured again the second and fourth nights with no further daytime O3 exposure. In California black oak, nighttime transpiration was elevated after chronic, moderate O3 exposure (1.8 fold increase over background). A one hour acute O3 exposure yielded no significant effects on nighttime transpiration. In blue oak, chronic O3 exposure significantly increased nighttime transpiration (2 fold increase over control leaves). Acute, short term O3 exposure had an even greater effect on nighttime transpiration (3 fold increase over control leaves). Chronic O3 exposure may elevate antioxidant concentrations, permitting some protection against short term, acute O3 exposure, because there were no synergistic effects of acute O3 exposure in plants previously exposed to chronic treatments in either oak species. Both species had a “threshold” O3 concentration of a one hour exposure to 150 ppb. One hour O3 exposures greater than 150 ppb increased nighttime transpiration linearly. Different O3 metrics will be used to present threshold responses, including O3 exposure (dose, O3 concentration x time), calculated O3 uptake (O3 concentration x gs x constant to convert diffusivity of water to O3), and measured O3 uptake (using the HOC system). When elevated nighttime transpiration was elicited, the response lasted for two nights after exposure. (literal)
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  • -US Forest Service, Pacific Southwest Research Station, Forest Fire Laboratory, Riverside, California -Istituto per la Protezione delle Piante, CNR, Firenze (literal)
Titolo
  • Quantifying short term O3 exposure effects on the level of nighttime transpiration. (literal)
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