Citogenotoxicidade, fenólicos totais e crescimento de Pfaffia glomerata (Spreng.) Pedersen cultivada sob concentrações de cobre e zinco

Abstract

Pfaffia glomerata (Spreng.) Pedersen, a native medicinal species, possesses the ability to accumulate metals, which can alter its production of metabolites and consequently their medicinal capacity. The objective of this study was to evaluate the influence of zinc and copper concentrations on growth, root biometry and the photosynthetic process of P. glomerata, as well as its influence on the production of phenolic compounds and cytogenotoxicity of leaf and root extracts of this species. In vitro clonal propagation of a genotype of P. glomerata and the acquired explants used for greenhouse experimentation were carried out. Seven treatments were used, one consisting of culture with ideal nutrient solution (2 μM of zinc and 0.5 μM of copper), three in solutions with excessive levels of zinc (50, 75 and 100 μM) and three with excess of copper (20, 40 and 60 μM). Two collections were performed at 63 and 84 days after the beginning of the treatments. The second collection plants were also used for the analysis of photosynthetic parameters and root biometry, and the acquisition of fresh and dry matter mass. For the cytotoxotoxicity test, dry leaves and roots of both collections were used and from this material 10g.L-1 aqueous extracts were prepared using the Allium cepa test system. The Folin-Ciocalteau technique was used to determine total phenolics in extracts from the second collection. The data obtained were statistically analyzed using the Scott-Knott test at the 5% level of significance. Concentrations of zinc and copper did not directly influence the antiproliferative capacity of leaf extracts of P. glomerata. With respect to root preparations, the experiments showed variations, since roots treated with zinc presented antiproliferative capacity and the same does not occur for extracts prepared with the roots of plants grown under copper concentrations. Physiological age was not significant for cytotoxicity and the extracts were not genotoxic. For the concentration of phenolic compounds, a very high concentration (between 180.3 and 291.05 mg EAG\L-1) was observed in the leaf extracts, but was reduced by up to 20 times for both occasions in the root extracts . The analysis of root biometry was performed with 25% of the root system and it was noticed that copper and zinc interfered in the development of the roots, since at the levels of 50 and 75 μM of zinc only the root diameter remained unchanged. Copper in turn reduced root length at all concentrations tested and the surface area at 40 and 60 μM. The biomass production, mainly of the aerial part, was affected, mainly in levels of 75 and 100 μM of zinc and 60 μM of copper. P. glomerata had rates of transpiration and assimilation, stomatal conductance, water use efficiency and carboxylation affected by zinc, unaffected by copper. It is concluded that the copper and zinc concentrations tested do not influence the cytogenotoxicity capacity of P. glomerata, but interfere in its growth and development.