Biofortificação e toxidez por selênio e fitoextração de cádmio em plantas de jambu cultivadas em hidroponia.

Abstract

Jambu is a plant native to tropical regions, mainly from the Brazilian Amazon, and widely used in regional cuisine. The objective of the thesis research was to analyze the behavior of jambu [Acmella oleracea (L.) R. K. Jansen] regarding its toxicity, biofortification and phytoextraction capacity. The experiments were individualized for toxicity and biofortification by Selenium (Se) and phytoextraction and tolerance to Cadmium (Cd). The experimental designs were completely randomized and carried out in a greenhouse using a hydroponic system. The first experiment analyzed the physiological, biometric and Se content behavior and had 4 treatments and 15 repetitions, totaling 60 plants. Three doses of selenium were used in the form of sodium selenate (5, 10 and 20 mg.L-1), plus the control (zero of Se). The second experiment evaluated the biofortification potential and had 6 treatments and 5 repetitions, using selenium, also in the form of selenate, with doses of 1, 2, 3, 4 and 5 mg.L-1 and more control. The third experiment evaluated the phytoextraction capacity, tolerance and Cd content in jambu and was developed with 5 treatments and 6 plants per treatment. The doses used were 1, 3, 6 and 9 mg.L-1, plus control (zero of Cd). Data were submitted to ANOVA, construction of multivariate indicators and composition of the regression model. In the Se toxicity experiment, the morphophysiological data showed a beneficial effect for the plant up to 5 mg.L-1, with a content of 462.15 µg.kg-1 of Se in the aerial part. From 10 mg.L-1 of Se, the plant starts to show signs of toxicity up to a lethal dose of 20 mg.L-1. With the use of multivariate indicators, it was possible to have a broader view of the dose/response relationship and to estimate, through regression models, the concentration of 2.95 mg.L-1 of Se in the solution, as the optimal dose for the best performance of the jambu. The second experiment showed that jambu obtained its greatest agronomic performance when supplemented with up to 3 mg.L-1 of Se. A more systemic analysis of the multivariate indicators showed that between 2.77 and 3.36 mg.L-1 of Se the jambu absorbed more nutrients, optimized its growth and mass gain. Based on the multivariate general indicator, the ideal dose for biofortification for human nutrition purposes was 2.98 mg.L-1 Se, where the daily consumption of 100g of biofortified jambu will provide 50.13 µg.day-1 of Se , making available to the population the amount of the element necessary for a balanced diet. The third experiment showed that in small doses (1 and 3 mg.L-1), the plant showed mass gain and greater photosynthetic performance, but from 6 mg.L-1 onwards this effect is inverse. Jambu is not a Cd hyperaccumulating plant, but it is tolerant to the metal, even presenting a hormetic effect. After 28 days of exposure to 1mg.L-1 of Cd in nutrient solution, the plant concentrated in its aerial part 1.35 mg.kg -1 of Cd, a value 6.5 times higher than that allowed by ANVISA for leafy vegetables. The research allowed us to conclude that jambu is tolerant and phytoextractor of Cd and can be biofortified to increasing doses of Se, as long as daily consumption limits and plant toxicity levels are respected.