Anatomia e histoquímica das folhas e caule de quatro espécies de Ipomoea L. (CONVOLVULACEAE).

Abstract

Ipomoea L. is the largest genus of Convolvulaceae family, with approximately 605 species and wide Neotropical distribution. It is characterized by presenting species with herbaceous habit and twining vines, with food, agricultural, ornamental and medicinal importance. Due to the morphological variability displayed, the distinction between species of Convolvulaceae using only morphological characters becomes quite difficult. In this sense, this present work aimed realized anatomical and histochemical descriptions of leaves and stems of four species of Ipomoea L. (Ipomoea bahiensis Ex. Roem & Schultz, I. nil Roth, I. setosa Ker Gawl and I. triloba L.), to recognize useful characters that provide grants for identification and delimitation of taxa. Anatomical analysis they were carried on fresh and hydrated leaves and stems, subsequently submitted to plant anatomy techniques and histochemical tests for evidenciation of different compounds. Some anatomical characteristics are similar between species as leaf blade anfihipoestomatic, paracytic stomata, unistratified epidermis, mesophyll dorsiventral with two layers palisade, biconvex midrib with one central vascular bundle, angular collenchyma, bicollateral vascular bundles and crystal idioblasts containing druses. However, some foliar characters were distinctive: indument, trichome types, contour of epidermal cells and number of vascular bundles in the petiole. The stem in secondary growth showed the same pattern refered for other species of Ipomoea, which has circular in outline, central cylinder with structure sifonostelic amphyphloic continuous, with bundles of sclerenchyma at the periphery of the external phloem, and the presence of channels laticifers in the cortical region, It is the angular chollenchyma evidenced in I.nil a diagnostic feature to separate it from other species. The epidermis is uniseriate, covered by a thick and striate cuticle in I. bahiensis, I. triloba and I. setosa, smooth and thin in I. nil. The histochemical tests showed the presence of starch, cutin, calcium oxalate crystals, and lignin and phenolic compounds. The anatomy of the leaf epidermis, the indumentum, the number of vascular bundles in the petiole, with the ornamentation of the cuticle in the stem were one of the distinctive characters between species.