Diurnal changes in photosynthetic parameters of Populus tremuloides, modulated by elevated concentrations of CO2 and/or O3 and daily climatic variation.
The diurnal changes in light-saturated photosynthesis (Pn) under elevated CO(2) and/or O(3) in relation to stomatal conductance (g(s)), water potential, intercellular [CO(2)], leaf temperature and vapour-pressure difference between leaf and air (VPD(L)) 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 g(s) and decreased Rubisco carboxylation efficiency, Vc(max). As a result of increasing VPD(L), g(s) decreased. Elevated [CO(2)] resulted in more pronounced midday decline in Pn compared to ambient concentrations. Moreover, this decline was more pronounced under combined treatment compared to elevated CO(2) treatment. The positive impact of CO(2) 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.
Institute of Ecology and Earth Sciences, University of Tartu, Estonia. katre.kets@gmail.com
Katre
K
Kets
Joseph N T
JN
Darbah
Anu
A
Sober
Johanna
J
Riikonen
Jaak
J
Sober
David F
DF
Karnosky
D002245:Carbon Dioxide / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D002940:Circadian Rhythm / Q000187:drug effects*; D057231:Climate Change; D010126:Ozone / Q000378:metabolism / Q000633:toxicity*; D010788:Photosynthesis / Q000187:drug effects*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D054046:Plant Stomata / Q000378:metabolism; D032107:Populus / Q000187:drug effects* / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects; D014867:Water / Q000378:metabolism
D014867:Water; D002734:Chlorophyll; D002245:Carbon Dioxide; D010126:Ozone