Selenium and silicon reduce cadmium uptake and mitigate cadmium toxicity in Pfaffia glomerata (Spreng.) Pedersen plants by activation antioxidant enzyme system

Cadmium (Cd) is toxic to plants and animals, making it necessary to develop strategies that seek to reduce its introduction into food chains. Thus, the aim of this study was to investigate whether silicon (Si) and selenium (Se) reduce Cd concentrations in Pfaffia glomerata medicinal plant and attenuate the oxidative stress promoted by this metal. These plants were cultivated in hydroponics under the following treatments: control (nutrient solution), 2.5 μM Se, 2.5 mM Si, 50 μM Cd, 50 μM Cd + 2.5 μM Se, 50 μM Cd + 2.5 mM Si. After 14 days of exposure to treatments, leaves and roots were collected for the determination of dry weight of shoot and roots, Cd concentrations, chlorophyll and carotenoids content, and biochemical parameters (lipid peroxidation and guaiacol peroxidase and superoxide dismutase activities). The data were submitted to analysis of variance and means were compared with Scott-Knott test at 5% error probability. Roots of P. glomerata plants showed a significant reduction on dry weight accumulation when exposed to Cd. However, both Se and Si promoted a significant reduction of deleterious effects of Cd. The Cd concentrations in the tissues were reduced in the presence of Se or Si. Plants treated with Cd together with Se or Si presented higher pigment content than those with only Cd, thus showing a reduction in the negative effects caused by this element. In the treatments in which Se and Si were added in the growth medium together with Cd, an activation of superoxide dismutase and guaiacol peroxidase enzymes was observed in the roots and shoot, which may have contributed to lower lipid peroxidation. Thus, Se and Si reduce Cd concentrations and have potential to ameliorate Cd toxicity in P. glomerata plants, which can be used to increase productivity and quality of medicinal plants.