Background and Objectives
Among the major environmental pollutants, lead is the most substantial contaminant due to causing toxicity in plants and organisms. Recently, the remediation of these metals has been considered in plants. Plant in vitro culture is a key tool in phytoremediation research. In general, Plant tissue culture and in vitro selection techniques are used to increase the tolerance and the accumulation of heavy metals which have been reported in numerous plant species and populations. The application of ornamental plants for phytoremediation in metal-contaminated soil is a new alternative. Ornamental kale is an important bedding plant in many landscapes of cold temperate regions. The present study was aimed to evaluate the Pb resistance and remediation of Brassica OleraceaVar. Acephala affected by in vitro culture as a bedding plant. This experiment was carried out in 2016 at Arak University.
Materials and Methods
In this study, the stalk explants of Brassica OleraceaVar. Acephala was used for callus induction. Callus and plantlet were exposed to different concentrations of lead in the media. The Callus induction medium was MS (Murashige and Skoog) supplemented with 0.1 mgL-1 2,4-D and BA. The regeneration medium was MS medium supplemented with 0.5 mgL-1 NAA in combination with 1 mgL-1 BA. The rooting medium was half-strength MS medium without plant growth regulators and sucrose. All of the media containing 30 gL-1 sucrose, 7 gL-1 agar, and pH were adjusted to 5.8. All of the regeneration stages from callus induction to rooting and the acclimatization stages were done by different concentration of Pb(NO3)2 (0, 10, 25, and 50 mgL-1). The traits, such as callus browning, fresh and dry weight, callus formation, survival rate, root and shoot length, leaf number, and the lead accumulation, were evaluated during various stages of callus regeneration and rooting in plantlets. A Completely Randomized Design (CRD) arrangement with three replications was used in this experiment. Data were analyzed using the ANOVA procedure of SAS statistical software (version 9.2).
Based on the results, not only did different concentrations of lead not have the toxic effects but also they had a stimulation effect in some concentrations on callus growth and regeneration. Lead concentrations increased leaf number and length of shoots in the regenerated ornamental kale. Lead accumulation in cultures was increased by increasing the concentration of lead in the medium at all stages of the regeneration. The highest accumulation of Pb was obtained 2395.7 ppb in callus treated by 25 mg L-1 Pb in media.
The results of the present study showed the occurrence probability of the somaclonal variation due to 2,4-D supplemented in the media. In the regenerated plant, results revealed that the growth traits and Pb uptake were affected by Pb concentrations. Some in vitro derived plantlets showed an increase in uptake potential of lead in their organs (6.1 to 2.7 times compared to the control) and that it is remarkable and suitable for phytoremediation studies.