Baru (Dipteryx alata Vogel), a woody species characteristic of Cerrado and its phytoremediation potential

Abstract

Baru (Dipteryx alata Vogel) is a native tree plant, widely distributed in Brazil, and has a growth and development in acidic soils like Cerrado, indicating a probable tolerance to adverse soil conditions, such as the high concentration of metals and the acidic pH. Due to the lack of information about the tolerance of this species to metals and the possibility of being used in the recovery of degraded areas and/or in phytoremediation, this work was developed with the objective of evaluating the in vitro germination and growth capacity of baru in medium supplemented with different concentrations of aluminum, iron, and manganese, as well as through chemical analysis, to determine the concentration of metals accumulated in cultivated plants in these conditions. The treatments consisted in different concentrations of metals: aluminum, Al³⁺ (0, 3.5, 7.0, 10.5, 21.0, or 42.0 mg L⁻¹); iron, Fe³⁺ (0, 2.5, 4.9, 7.4, 14.7, or 29.4 mg L⁻¹); and manganese, Mn²⁺ (0, 0.4, 0.8, 1.2, 2.4, or 4.8 mg L⁻¹) added to the medium WPM. The tested values were based on using the lower concentration as the limit value, calculated based on risk to human health in accordance with CONAMA resolution 420/2009 for groundwater. At 60 days of cultivation, the percentage of germination, the average number of leaves, the length of the main root and the aerial part, the fresh and dry mass of the aerial part and the root system and the cations concentration Al³⁺, Fe³⁺ and Mn²⁺ in the plant biomass, were evaluated. The results showed that under the conditions in which the experiment was conducted, germination and in vitro growth of baru were not affected by the presence in high concentrations of any of the evaluated metals, with no differences in the percentage of germination and plant growth, as well as typical toxicity characteristics were not observed, such as changes in root morphology, chlorosis, or tissue oxidation. The absence of toxicity symptoms in baru plants, in the presence of Al³⁺, Fe³⁺, and Mn²⁺, indicate that the species is tolerant to these metals. The accumulation of Al³⁺ and Fe³⁺ in the plant biomass at the beginning of growth, simultaneously with the increase in the concentrations of these elements in the culture medium, indicates that this species can be used for phytoremediation, because it is a probable accumulator of these elements throughout its development, given the presence in significant concentrations of these elements also in the seeds.