Superfície e Estrutura Foliar de Três Espécies do Gênero Ipomoea L. (Convolvulaceae) Ocorrentes na Canga Hematítica de Carajás, Pará

Abstract

Ipomoea cavalcantei Austin, I. marabaensis Austin & Secco and I. carajasensis Austin are endemic species that flourish on iron ore rocks of the hematitic canga of Carajás, Pará. However, there are few studies of leaf anatomy related to these species. In view of this, this work aims to know the surface and cellular organization of the leaves, aiming to separate the taxa. The samples were taken from exsiccata of the MG herbarium (N° 85741; N° 117008 and 'N° 85763, respectively) and submitted to the usual techniques in the plant anatomy laboratory. Morphologically, I. cavalcantei is a scandent shrub; 4 m tall; leaves measure 4 to 6 in length and 1 to 2.5 cm wide, these are elliptic: apex obtuse, rarely acuminate; base cuneate to obtuse, I. marabaensis is a vine in clumps of 1.5 m high, obtuse leaf, reticulate vein, leaf lamina measuring 3 to 5 in length and 0.5 to 1.5 in width. I. carajasensis is a liana, sagitate leaf, acuminate apex, reticulate vein, leaf lamina measuring 2 to 3 cm long and 1 to 2 cm wide. Anatomically, the leaf surfaces of the three species showed heterodimensional cells, sinuous anticlinal walls, ornamented cuticle, amphistomatous limb, paracitic stomata, filiform tector trichomes (I. marabaensis and I. carajasensis, visibly in greater quantity on the adaxial surface, whereas in I. cavalcantei they are adpressed), glandular trichomes are also present in the epidermis of the three species. In cross section the taxa have dorsiventral mesophyll, with about three to four layers of palisade parenchyma and with the presence of drusks distributed along the mesophyll. The central vein presented distinct in each species, for I. cavalcantei a ventrally convex curvature was observed, in I. marabaensis the ventral axis is said to be straight, whereas in I. carajasensis a ventrally concave curvature is seen. The vascular bundles are collateral, with the presence of collenchyma attached to the adaxial and abaxial epidermis, respectively. The studied species present similarities among themselves, however, it was possible to differentiate them by the following structures: type of trichomes and shape of the central vein.