We have explored leaf-level plastic response to light and nutrients of Quercus ilex and Q. coccifera, two closely
related Mediterranean evergreen sclerophylls, in a factorial experiment with seedlings. Leaf phenotypic plasticity,
assessed by a relative index (PI = (maximum value - minimum)/maximum) in combination with the significance
of the difference among means, was studied in 37 morphological and physiological variables. Light had significant
effects on most variables relating to photosynthetic pigments, chlorophyll fluorescence and gas exchange, whereas
nutrient treatment had a significant effect in only 10% of the variables. Chlorophyll content was higher in the
shade whereas carotenoid content and nonphotochemical quenching increased with light. Nutrient limitations
increased the xanthophyll-cycle pool but only at high light intensities, and the same interaction between light and
nutrients was observed for lutein. Predawn photochemical efficiency of PSII was not affected by either light or
nutrients, although midday photochemical efficiency of PSII was lower at high light intensities. Photosynthetic
light compensation point and dark respiration on an area basis decreased with light, but photosynthetic capacity
on a dry mass basis and photochemical quenching were higher in low light, which translated into a higher nitrogen
use efficiency in the shade. We expected Q. ilex, the species of the widest ecological distribution, to be more plastic
than Q. coccifera, but differences were minor: Q. ilex exhibited a significant response to light in 13% more of the
variables than Q. coccifera, but mean PI was very similar in the two species. Both species tolerated full sunlight
and moderate shade, but exhibited a reduced capacity to enhance photosynthetic utilization of high irradiance.
When compared with evergreen shrubs from the tropical rainforest, leaf responsiveness of the two evergreen oaks
was low. We suggest that the low leaf-level responsiveness found here is part of a conservative resource use
strategy, which seems to be adaptive for evergreen woody plants in Mediterranean-type ecosystems.