This research aimed to study the leaf anatomy of the weed species Nicandra physaloides, Solanum viarum, Solanum americanum and Raphanus raphanistrum to acquire a better understanding of the barriers each species imposes upon herbicide penetration. Completely expanded leaves from the third to the fifth node were collected from plants spontaneously occurring in field. Three samples, with approximately 1 cm², were taken at the central portion of the leaves in each species. These samples were used in structural studies, clarification and observation using a scanning-electron microscope (SEM). All species are amphistomatic. The main leaf barrier against herbicide penetration in N. physaloides was high trichomic density, whereas in S. viarum, the main barriers were low stomatic density in the adaxial side, high trichomic density, high content of epicuticular wax and high cuticle thickness. S. americanum's main leaf barriers were low stomatic density and high cuticle thickness in the adaxial side. High cuticle thickness in the adaxial side was the only barrier observed in leaves of R. raphanistrum.
cuticle; epicuticular wax; stomata; trichome; vascular bunches
