Selênio como amenizador do estresse induzido por cádmio em milho (Zea mays L.).

Abstract

Cadmium (Cd) is in one of the most toxic heavy metals that occurs in the environment, is easily absorbed by plants, even at low concentrations is able to cause impaired photosynthesis and inhibition of growth. Among the alternatives to solve the problems induced by Cd contamination, there is the use of attenuators such as selenium (Se), which is considered a beneficial element for plants, which can increase their tolerance to various biotic and abiotic stresses. The aim of this study was to evaluate the effect of Se on growth, biochemical aspects and physiological responses of corn under stress conditions by Cd. Hybrid corn seeds (K9606 VIP 3) were treated with sodium selenite (Na2O3Se) in concentrations of 0.0; 1.5; 3.0 and 5.0 mg L-1 Se and subjected to two different experiments containing Cd dosages (0.0; 1.3; 3.0 and 4.5 mg L-1). In the first, the following were evaluated: the root length (RL); the aerial part length (APL); dry root matter (DRM), dry shoot matter (DSM), dry total matter (DTM and concentrations of total soluble carbohydrates (TSC), sucrose and proline in leaves and roots. In the second, it was evaluated: the net CO2 assimilation rate (A); stomatal conductance (gs); sweating (E); intercellular CO2 concentration (Ci); instant carboxylation efficiency (EiC A / Ci); instant water use efficiency (USA); carotenoid contents; chlorophyll a (Chl a), b (Chl b) and total (Chl). The experimental design was completely randomized in a 4 x 4 factorial scheme, with four replications. The presence of 4.5 mg L-1 Cd reduced RL, APL, DRM, TSC, A, EiC, the levels of Chl a, Chl b and Chl and promoted increases in the concentrations of proline and sucrose in the roots and leaves and in the levels of carotenoids. In general, the pretreatment with Se before exposure to Cd promoted an increase in RL, APL, in the production of DRM and DSM, mitigated the deleterious effects induced by Cd, through increases in the levels of proline, sucrose and TSC in the leaves , Chl a, Chl b and Chl and reduction in carotenoids, mainly at the dose of 5 mg L-1 of Se.