Potencial fitorremediador do mogno brasileiro (Swietenia macrophylla King) em exposição ao níquel: respostas anatômicas, bioquímicas, antioxidantes e NDVI

Abstract

The advancement and intensification of industrial and mining activities has generated a series of impacts on natural ecosystems, combined with the inappropriate use of agrochemicals and the erroneous disposal of electronic products, contributing to the contamination of soils with a variety of chemical elements, including heavy metals. Because of this, this work aimed to evaluate the effect of increasing nickel dosages on germination, vegetative growth, anatomy, biochemistry, oxidative system and the normalized difference vegetation index (NDVI) of Brazilian mahogany (Swietenia macrophylla), seeking indicate the potential use of this species in phytoremediation programs for soils contaminated with heavy metals. Seeds were cultivated in polyethylene trays containing sand and kept at a constant temperature of 28°C, 90% relative humidity and a 12-hour photoperiod for 43 days. The experimental design used was randomized blocks (DBC), with five treatments (0, 2, 4, 6 and 8 mg.L-1 of NiCl2.6H2O), with six replications. Data were subjected to analysis of variance (ANOVA) and means were tested for significant differences by Tukey test using R-Studio-1.3.1093 software. Changes were observed in plant growth and biomass under different nickel concentrations, as well as anatomical changes in different organs, where initially a significant difference was seen in the central region of the leaf, in the stem and in the root. The NDVI index and total carbohydrate concentration did not show statistical differences with the application of nickel, but changes were observed in photosynthetic pigments, reducing sugars and sucrose as an adaptive form to nickel. Furthermore, with the increase in nickel dosages, the synthesis of ammonium, amino acids and proline in the root also increased, in contrast, the synthesis of glycine decreased. In the leaf, however, the increase in metal tends to increase only the concentration of amino acids and decrease the concentration of glycine, while ammonium and proline production are not significantly affected by nickel. The plant antioxidant defense system was efficient to attenuate the toxic effects of ROS at different nickel concentrations, with significant actions of CAT and SOD enzymes in the root, while in the leaf it had the main action of APX and CAT. The cultivation of mahogany plants can be defended to mitigate Ni pollution in these areas, since this forest species has a particular characteristic of resistance to stress conditions in contact with the heavy metal.