Studies on the Quercus hybrids in Sicily: leaf micromorphology and xylem structure in Quercus × fontanesii Guss.

In order to find new suitable characters in the taxonomic delimitation of the genus Quercus, whose hardness is well known, Quercus x fontanesii, endemic to Sicily, has been studied in comparison with its parents, i.e. Q. gussonei, wich is close to Q. cerris, and Q. suber. These taxa are here delimited as far as taxonomy, ecology, and Sicilian distribution are concerned. Furthermore, the results of SEM microstructure analysis of leaves and xylem anatomy are illustrated and commented. The analysis of the leaf microstructures shows that there is a remarkable similarity between the stomata and stellata trichomes of Q. x fontanesii and both the parental species, as the trichome rays are numerically intermediate in the nothotaxon. Also xylem anatomy in Q. x fontanesii results intermediate between both the parents. In particular, the qualitative analysis of the transverse sections on earlywood and latewood show that the vessel distribution in Q. xfontanesii gives origin to a structure with intermediate features between a diffuse porous wood (Q. suber) and a ring porous wood (Q. gussonei). The quantitative analysis, based on the maximum and minimum diameter, surface and shape factor, confirms the conclusion stated above. In particular, the minimum diameter of the wood vessels is the most significant parameter. The frequency distribution shows an increase in the number of vessels in Q. xfontanesii, from earlywood to latewood, differently from the two parental species.