Photoprotection mechanisms in Quercus ilex under contrasting climatic conditions

Acclimation to local conditions may produce adaptive responses in plants subjected to diverse climatic stresses. However, it has not been assessed how local adaptation and phenotypic plasticity contribute to photoprotection mechanisms in response to contrasting climatic conditions in Mediterranean tree species.We analyzed photoprotection mechanisms in mature trees of the Mediterranean evergreen oak Quercus ilex at three sites with contrasting climatic conditions, i.e. xeric, continental and mesic sites. We studied morphological and physiological parameters indicative of photoprotection in adult trees in the field. In order to establish whether these parameters were genetically determined we compared adults with seedlings germinated from acorns of the three sites and grown under common greenhouse conditions.In the field we found no significant differences in most of the physiological parameters in summer, but in winter the adult trees from the continental site were photoinhibited. In contrast, there were significant differences between seedlings in most photoprotective parameters evaluated. Morphological traits such as trichome density and leaf reflectance differed between populations, both in field-grown trees and in greenhouse-grown seedlings, being higher in all cases in plants from the xeric site than elsewhere. Our findings suggest the existence of constitutive differences in leaf photoprotection mechanisms among Q. ilex populations. These divergences may represent an inherent source for more stress tolerant ecotypes in the face of changing climatic conditions.