Phytoremediation potential of Brassica juncea Ac. 1774 for mitigation of Cu (II) and As (V)
No Thumbnail Available
Date
2015
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Uva Wellassa University of Sri Lanka
Abstract
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).
Description
Keywords
Science and Technology, Technology, Environmental Science, Plant Biology, Plant, Genetics