Morphological and molecular diversità among Italian populations of Quercus petraea (Fagaceae)

Differences in phenotypic plasticity among six populations of Quercus petraea exposed to drought stress were examined. The study was performed as a common garden experiment with five-year-old seedlings in a greenhouse and a total of 13 morphological and micromorphological characters were scored for 24 seedlings from each population, in both control and droughted environments. The populations studied showed considerable differentiation for trait means while maintaining several of the morphological differences observed in the field. Since these differences in morphology were found in populations growing under the same conditions, it is probable that these are due to genetic differences. However, a high degree of phenotypic variation was found with significant population × water treatment interactions. Overall, this study shows that the origin of sessile oaks (xeric or mesic stands) determines the variation in phenotypic plasticity when plants are compared under different water regimes.