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    Author(s): Katre Kets; Joseph N.T. Darbah; Anu Sober; Johanna Riikonen; Jaak Sober; David F. Karnosky
    Date: 2010
    Source: Environmental Pollution. 158(4): 1000-1007.
    Publication Series: Scientific Journal (JRNL)
    Station: Northern Research Station
    PDF: View PDF  (424.87 KB)


    The diurnal changes in light-saturated photosynthesis (Pn) under elevated CO2 and/or O3 in relation to stomatal conductance (gs), water potential, intercellular [CO2], leaf temperature and vapour-pressure difference between leaf and air (VPDL) were studied at the Aspen FACE site. Two aspen (Populus tremuloides Michx.) clones differing in their sensitivity to ozone were measured. The depression in Pn was found after 10:00 h. The midday decline in Pn corresponded with both decreased gs and decreased Rubisco carboxylation efficiency, Vcmax. As a result of increasing VPDL, gs decreased. Elevated [CO2] resulted in more pronounced midday decline in Pn compared to ambient concentrations. Moreover, this decline was more pronounced under combined treatment compared to elevated CO2 treatment. The positive impact of CO2 on Pn was relatively more pronounced in days with environmental stress but relatively less pronounced during midday depression. The negative impact of ozone tended to decrease in both cases.

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    Kets, Katre; Darbah, Joseph N.T.; Sober, Anu; Riikonen, Johanna; Sober, Jaak; Karnosky, David F. 2010. Diurnal changes in photosynthetic parameters of Poulus tremuloides, modulated by elevated concentrations of CO2 and/orO3 and daily climatic variation. Environmental Pollution. 158(4): 1000-1007.


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    Photosynthesis, Stomatal conductance, Vapour-pressure difference, Environmental stress, CO2/O3

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