Comparative morphology and anatomy of the leaf and stem of species of Zanthoxylum (Rutaceae) from central Argentina

Abstract

Zanthoxylum is one of the major genera of Rutaceae with at least 200 species in tropical and temperate regions worldwide. In Argentina is represented by 10 species, two of them inhabiting in the central region, the native Zanthoxylum coco and the naturalised Zanthoxylum armatum var. armatum. These species are found in xerophytic deciduous forests of Chaco biogeographic province. Besides the floristic and ethnobotanical importance of these species, their leaves and stems have been scarcely studied. The objective of this contribution was to present a comparative morphological and anatomical study of the leaves and young stems of the species of Zanthoxylum from central Argentina. The analysis was done using herbaria vouchers, freshly collected and fixed material. The species share morphological features, as armed stems, leaves alternate, odd-pinnately, 3- to many foliolate. The main differences are that Z. armatum is an evergreen shrub with axillar inflorescences whereas Z. coco is usually a deciduous tree with terminal inflorescences. Both species also share the presence of secretory cavities, glandular trichomes and hypostomatic leaves. However each species presents particularities of the leaves structure that could be important and related to the environment that the plants develop.