Browsing by Author "Herath, H.M.S.D."

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    Phytoremediation potential of Brassica juncea Ac. 1774 for mitigation of Cu (II) and As (V)
    (Uva Wellassa University of Sri Lanka, 2015) Herath, H.M.S.D.; Wijesekara, K.B.
    Phytoremediation is an emerging technology that employs the use of higher plants to clean up contaminated environments. Use of plants to extract toxic metals from contaminated soil and water, has emerged as a cost-effective, environment-friendly clean up alternative. In Sri Lanka large areas of soil and water contain high levels of heavy metals such as Cd, Cu, Co, Ni and Zn and other pollutants (Dissanayake et al., 2002). Members of the Brasicaceae are promising candidates for phytoextraction of metals (Kumar et al. (1995, Weerakoon and Somaratne, 2009).Sri Lanka has genetically diverse mustard (B. juncea (L.) Cazen) germplasm of over sixty accessions (PGRC Catalogue, 1999) and their true phytoextarctive potentials are yet to be determined. Most of the previously reported research on phytoremediation has conducted in vivo using soil to establish plants. Use of soil which is a highly heterogeneous medium could not unveil the true phytoremediation potential of plants due to micro-variations in the composition of soil. Hence, this study was performed in vitro and the plants were grown in well-defined plant tissue culture media where all other physical parameters such as light intensity and relative humidity were kept constant. The main objectives of this study was to investigate the maximum accumulation level of copper Cu (II) and Arsenic As (V) by in vitro raised plants of Brassica juncea Ac:1774 which has already been identified as a hyper- accumulator of Cr (VI) and multiple metal bio-accumulator (Wijethunghe et al., 2010). Methodology Authenticated seed samples of Brassica juncea (Indian mustard) of AC: 1774 was obtained from the Plant Genetic Recourses Centre (PGRC) at Gannoruwa, Sri Lanka. Seeds were surface sterilized by rinsing with a 10% solution of commercial bleach for 5 min followed by rinsing with 70% ethanol solution for 2 min and three times through washings with sterilized distilled water. Sterilized seeds were briefly dried on filter papers and cultured on solid MS (Murashige and Skoog, 1962) media. One week old seedlings were transferred on to a wick placed in liquid MS media in 15 cm culture tubes supplemented with 0, 50, 150, 200 ppm Cu (II) and 0,5, 15, 25 ppm As (V) separately. Seedlings were allowed to grow for three weeks in this medium. After that plantlets were removed, washed with tap water and dried in an oven. Dried platelets were grounded separately to obtain a fine powder which was acid digested following dry-ash-method and the accumulated heavy metal concentration for each sample was determined using Atomic Absorption Spectrometer (Varian, Australia). Each treatment had three replicates within an experiment and each experimented was repeated three times. Result and Discussion Plants of Brassica juncea Ac:1774 demonstrated relatively a high bioaccumulation of two heavy metals tested, As (V) and Cu (II). For As (V) the maximum tolerance level was 25 ppm while for Cu (V) it was 150 ppm (Fig 1 and 2). Plants showed a significantly (p≤ 0.05) higher Cu (II) toleranc e than As (V). At high concentrations plants showed signs of necrosis and retarded growth due to toxic effects of As (V). There was no significant effect by replication (Table 1 and 2) and this provides evidence that by growing plants in vitro, plant to plant variations as well as environmental effects could be kept at a minimum levels. Sings of toxicity was shown by plants after two to three days from transfer to MS media supplemented with high concentrations of heavy metals. The effect of AS (V) was prominent and physiological breakdown of plants is so fast. It has been reported that Arsenate replaces phosphate when taken up by plants that disrupts the production of ATP which results in sudden cell death. Also arsenic is inhibitory towards cell function because it reacts with sulfhydryl enzymes and disrupts their activity (Luongo and Ma, 2005).