Germinação e crescimento in vitro de baru (Dipteryx alata Vogel) em diferentes concentrações de alumínio, ferro e manganês

Abstract

Baru (Dipteryx alata Vogel) is a native tree plant, widely distributed in Brazil and has a growth and development in acidic soils like the Cerrado, indicating a probable mechanism of tolerance to adverse soil conditions, such as the high concentration of metals and the acidic pH. Due to the lack of information on 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 germination capacity and in vitro growth of baru in medium supplemented with different concentrations of aluminum, iron and manganese, as well as, through chemical analysis, determine the concentration of metals accumulated in seedlings grown under these conditions. The treatments consisted of: 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 values tested were based on the CONAMA 420/2009 resolution for groundwater, using the limit value as the lowest concentration, calculated based on risk to human health. A completely randomized experimental design was carried out, with six concentrations of each metal being tested, each treatment consisting of three replications, each repetition consisting of a cultivation bottle containing five seeds each. At 60 days of inoculation, 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 concentration of cations Al, Fe and Mn were evaluated in seedling biomass. 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 metals evaluated, with no differences in the percentage of germination and seedling growth, as well as typical toxicity characteristics, such as changes in root morphology, chlorosis or tissue oxidation, were not observed. The absence of toxicity symptoms in baru seedlings, in the presence of Al, Fe and Mn in concentrations above the limit values found in the legislation, indicate that the species is tolerant to these metals. The accumulation of Al and Fe in the seedling biomass, simultaneously with the increase in the concentrations of these elements in the culture medium, indicates that the species is a probable accumulator of these elements throughout its development, considering the presence in significant concentrations of these elements also in the seeds.