EFEITOS ANATÔMICOS NAS RAÍZES DE TALINUM PANICULATUM (JACQ.) GAERTN EXPOSTAS A DOSES CRESCENTES DE COBRE

Abstract

Copper (Cu) is an essential micronutrient for microorganisms and plants. It acts on various parts of plants, but in excess it can cause toxicity and, consequently, harm plant development. The root, the first organ to make contact with the metal, tends to accumulate it because its translocation to the aerial part of the plant tends to be slow. Thus, the objective of this work was to characterize possible anatomical effects on the roots of the species Talinum paniculatum exposed to different concentrations of Cu in the soil. The species was cultivated in a clayey Oxisol, with different concentrations of Cu (0, 50, 100, 200 and 400 mg dm-3 soil). After 60 days of growth, root samples were selected, fixed in FAA50, dehydrated and stored in 70% alcohol. Then, the samples were embedded in historesin; sectioned on a 7 µm rotating microtome; stained with toluidine blue or subjected to histochemical tests. The slides were mounted in Permount, analyzed and photographed. The diameter of the vessel elements was evaluated using Image J software. The roots of T. paniculatum showed the beginning of secondary growth, evidenced by the differentiation of the vascular cambium and replacement of the epidermis by the peridermis. The secondary xylem parenchyma cells accumulate starch and mucilaginous idioblasts are abundant in this region. Changes in the diameter of the xylem conductor cells were observed when exposed to concentrations of (0, 50, 100 and 200 mg dm-3 soil). On the other hand, at the highest concentration (400 mg dm-3 soil), the results are similar to the control plants, that is, the plant suffered a greater impact in the first doses of Cu and showed to be tolerant in higher doses. Thus, we can conclude that T. paniculatum is tolerant to copper since no structural changes were observed in the roots which could compromise plant growth and development.