LEAF ANATOMICAL AND VENATION PATTERN OF PIPER SPECIES FROM BRAZIL.
Anatomical traits. Germplasm. Leaf vein segmentation. Native species.
Among the essential oil-producing species of Piper L. present in Brazilian germplasm, Piper aduncum, Piper hispidinervum and Piper affinis hispidinervum stand out. Considering the morphological similarities between these species, this study focused on characterize and compare the leaf anatomy and venation pattern in these three species of Piper. The experimental design was completely randomised, with three treatments, five replications (visual fields in the microscope) and each repetition consisted of different numbers of histological sections of five individuals. Cross sections and paradermal sections of the leaf blade were obtained for the measure the anatomical structures visualized in light and scanning electron microscopy. The species had uniseriate epidermis, hypodermis with one to three layers of cells, mesophiles with oily and crystalline ideblasts, presence of glandular trichomes and tector trichomes, presence of tetracytic stomata, staurocytic and anisocytic stomata. The presence of stomata on both leaf faces is exclusive to P. affinis hispidinervum, while the uniseriate hypodermis on the abaxial face identifies P. hispidinervum and the rarity of glandular trichomes on the adaxial face of P. aduncum leaves is useful in their identification. There was variability in the density of trichomes on the adaxial face, with an average of 130.5, 219.8 and 212.6 no.tricomas.mm-2 for P. aduncum, P. hispidinervum and P. affinis hispidinervum, respectively. P. aduncum obtained the highest values for polar diameter (14.85 μm) and P. hispidinervum obtained the lowest values (13.63 μm). P. affinis hispidinervum had the highest stomatal density, around 246 stomata per unit area (mm2) evaluated. The leaves show pinnate primary nervation, camptodroma secondary nervation, eucamptodroma tertiary nervation, with fourth order veins. There are leaf traits for the identification and differentiation between Piper species. These leaf traits also provide information of the characterization that can be used in Piper breeding program.