Residual 2,4-D in plant tissue culture discarded media: a neglected source of environmental pollution

Abstract

The herbicide 2,4-D (2,4-dichlorophenoxyacetic acid) is a plant growth regulator for callus induction and somatic embryogenesis in tissue culture protocols. Research has shown that exposure to 2,4-D causes a number of environmental and health problems. Routine laboratory work involves the use of 2,4-D in the preparation of culture media, thus generating culture media with 2,4-D residues, the disposal of which is often improper. Therefore, this study aimed to determine the residual content of 2,4-D in MS (Murashige and Skoog), agrowth medium used in plant tissue cultures, after callus development. MS media were used from callus cultures of bananeira (Musa sp.) and basil (Ocimum basilicum L.). Callus cultures were supplemented with 2,4-D at concentrations of 1.0 and 0.5 mg.L-1, respectively. MS media were also evaluated in the absence of plant culture at the 0.2; 0.5 and 1.0 mg.L-1 concentrations of 2,4-D under light and dark conditions for a period of one month. Banana callus cultures consumed about 79% ± 0.27% of 2,4-D in the culture medium after two months. After three months of culture, it was not possible to detect 2,4-D in basil callus culture since the values found were below the detection limit (LOD ≤ 0.096 mg.L-1). Light does not appear to influence the degradation of 2,4-D in the culture medium. Results suggest that the concentration of 2,4-D residues depends on the species cultured. Improper disposal of these media might be a source of ignored and, hence, environmental contamination, depending on 2,4-D concentration and volume of media waste.