Leaf-level responses to light in two co-occurring Quercus (Quercus ilex and Quercus suber): leaf structure, chemical composition and photosynthesis

We studied morphological, biochemical and physiological leaf acclimation to incident Photon-Photosynthetic-Flux-Density ( PPFD ) in Quercus ilex (holm oak) and Quercus suber (cork oak) at Mediterranean evergreen oak woodlands of southern Portugal. Specific leaf area ( SLA ) decreased exponentially with increasing PPFD in both species. Q. ilex had lower SLA values than Q. suber . Leaf nitrogen, cellulose and lignin concentration (leaf area-based) scaled positively with PPFD . Maximum rate of carboxylation (V cmax ), capacity for maximum photosynthetic electron transport (J max ), rate of triose-P utilization (V TPU ) and the rate of nonphotorespiratory light respiration (Rd) were also positively correlated with PPFD in both Quercus species, when expressed in leaf area but not on leaf mass basis. Q suber showed to have higher photosynthetic potential (V cmax , J max m and V TPU m ) and a higher nitrogen efficient nitrogen use than Q.ilex . Leaf chlorophyll concentration increased with decreasing PPFD , improving apparent quantum use efficiency (Φ) in both Quercus species. We concluded that, in Q.ilex and Q.suber, leaf structural plasticity is a stronger determinant for leaf acclimation to PPFD than biochemical and physiological plasticity.