© 1994 Heron Publishing—Victoria, Canada
Relationship between CO2-dependent O2 evolution and photosystem II activity in oak (Quercus petraea) trees grown in the field and in seedlings grown in ambient or elevated CO2
Daniel Epron (1, 2, 3), Erwin Dreyer (1), Catherine Picon (1) and Jean Marc Guehl (1)
1. Laboratoire d'Ecophysiologie Forestière, Centre INRA de Nancy, 54280 Champenoux, France / 2. Laboratoire Ecologie Végétale, Université Paris Sud, 91405 Orsay cedex, France / 3. Author to whom correspondence should be addressed / Received September 24, 1993
Summary
The light-response of the apparent quantum yield of photosynthetic O2 evolution (ΦO2) under non-photorespiratory conditions was measured together with the photochemical efficiency of PS II (ΔF/Fm′), the photochemical efficiency of open PS II reaction centers (Fv′/Fm′) and the photochemical fluorescence quenching (qp) of leaf disks punched from oak leaves of seedlings grown in ambient (350 µmol mol–1) or elevated (700 µmol mol–1) CO2 in a greenhouse, and from sunlit leaves of mature oak trees (Quercus petraea (Matt.) Liebl.). There were marked differences between seedlings and trees. In seedlings, CO2 concentration during growth did not modify the light response of photosynthesis or PS II activity. There was a single linear
relationship between ΦO2 and ΔF/Fm′ in seedling leaves that was independent of the CO2 concentration imposed during growth. In contrast, this relationship was curvilinear in sunlit leaves of adult trees. In seedling
leaves, the decrease in qp (i.e., the proportion of open PS II reaction centers) largely accounted for the decrease in ΔF/Fm′, whereas the decrease in ΔF/Fm′ in sunlit leaves of mature oak trees was dependent on both qp and Fv′/Fm′.
Keywords:
chlorophyll fluorescence, gas exchange, photochemical efficiency, photosynthesis.
