Comparison of leaf morphoanatomy of Diodella radula (Willd. & Hoffmanns. Ex Roem. & Schult.) Delprete and Diodella teres (Walter) Small (Rubiaceae)

Diodella radula (Willd. & Hoffmanns. ex Roem. & Schult.) Delprete e Diodella teres (Walter) Small (Rubiaceae) are weeds found in agricultural areas from Mato Grosso do Sul and it is difficult to identify them on vegetative phase, so the morphologic and anatomic studies are an important instrument for controling the species. This work intended to characterize the leaf morphoanatomy of Diodella radula and D. teres, aiming to promote taxonomic subsidies and determine the structures which may influence on the herbicides absorption. The morphoanatomic studies were carried out with fresh material and fixed. Cross and paradermic sections of leaf blade were obtained. The cutting edges were dyed as an usual methodology and submitted to histochemical tests. These species are distinguished plants because they can stay in the sun; Diodella teres is frequently found on the edge of the roads, on a drier soil while D. radula is mainly found on dirty fields, damp soil and at the river banks. D. radula and D. teres leaves present general characteristics quoted for Rubiaceae family, as for example, unilayered epidermis, paracytic stomata, dorsiventral mesophyll and collateral vascular bundles. The observed characteristics such as epidermic cells, papilla size, glandular trichomes and collenchyma arrangement are distinct for both species and therefore they may be used as characters to bound the two species. The low density of stomata and the cuticle thickness on the adaxial surface observed in D. radula and D. teres seems to be leaf barrier to block the herbicides penetration.