Leaf structural features of Mediterranean perennial species: plasticity and life form specificity RAM KAILASH P. YADAV1, ARTEMIOS M. BOSABALIDIS2 and DESPINA VOKOU1 1 Department of Ecology, Faculty of Biology, University of Athens, Athens 157 84, Greece 2 Department of Botany, Faculty of Biology, University of Athens, Athens 157 84, Greece   Abstract We studied leaf structural traits of eight perennial Mediterranean species (Arbutus unedo, Quercus coccifera, Pistacia lentiscus, Myrtus communis, Lavandula stoechas, Cistus incanus, Calamintha nepeta, and Melissa officinalis) co-occurring in the same area and representing different life-form groups. In summer leaves, we measured the thickness of leaf lamina, cuticles and epidermises of adaxial and abaxial leaf surfaces, as well as of the palisade and spongy parenchymas. We also estimated the specific leaf mass (SLM), the density of stomata, the density of glandular and non-glandular hairs and the relative volumes of the leaf tissues and of the intercellular spaces of the mesophyll. While the evergreen-sclerophyllous species are characterized by thicker leaves, thicker cuticles, and more compact mesophyll, the seasonally dimorphic and the non-woody perennials bear hairs. All species had a high stomatal density on the abaxial leaf surface. Phenolic compounds were only observed in A. unedo, Q. coccifera and P. lentiscus. Well known features of xeromorphic leaves, like the development of the palisade tissue at the expense of the spongy one, were not found in the species examined; in the evergreen-sclerophyllous M. communis, in particular, there was an exceptional development of the spongy parenchyma over the palisade one. SLM, leaf thickness and relative contribution of the two mesophyll components show considerable plasticity enabling species to cope with different environmental regimes. Traits of presumably high discriminant value, like the sclerophylly index (SLM), cannot clearly separate the representatives of the different life-form groups.   < back .