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    Author(s): Asko Noormets; Olevi Kull; Anu Sober; Mark E. Kubiske; David F. Karnosky
    Date: 2010
    Source: Environmental Pollution. 158: 992-999.
    Publication Series: Scientific Journal (JRNL)
    Station: Northern Research Station
    PDF: Download Publication  (395.93 KB)


    The effect of elevated CO2 and O3 on apparent quantum yield (ø), maximum photosynthesis (Pmax), carboxylation efficiency (Vcmax) and electron transport capacity (Jmax) at different canopy locations was studied in two aspen (Populus tremuloides) clones of contrasting O3 tolerance. Local light climate at every leaf was characterized as fraction of above-canopy photosynthetic photon flux density (%PPFD). Elevated CO2 alone did not affect ø or Pmax, and increased Jmax in the O3-sensitive, but not in the O3-tolerant clone. Elevated O3 decreased leaf chlorophyll content and all photosynthetic parameters, particularly in the lower canopy, and the negative impact of O3 increased through time. Significant interaction effect, whereby the negative impact of elevated O3 was exaggerated by elevated CO2 was seen in Chl, N and Jmax, and occurred in both O3-tolerant and O3-sensitive clones. The clonal differences in the level of CO2 x O3 interaction suggest a relationship between photosynthetic acclimation and background O3 concentration.

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    Noormets, Asko; Kull, Olevi; Sober, Anu; Kubiske, Mark E.; Karnosky, David F. 2010. Elevated CO2 response of photosynthesis depends on ozone concentration in aspen. Environmental Pollution 158: 992-999.


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    electron transport, elevated CO2, elevated O3, interactive effects of elevated CO2, O3 and light, leaf photochemistry, light harvesting

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