In the 20th day Nickel accumulation was observed
that it was increased than the control plants. In this
period high accumulation was observed in the stem
part than roots and leaves. After 40th day root, stem
and leaf accumulations was increased and high
accumulation difference was observed in the leaf
part. After 60th day high accumulation was
observed in the leaf, stem and root almost doubled
than the 40th day accumulations, a high
accumulation difference observed in the root part.
(Table 2). After the experimental period nickel
accumulated in the order roots > stem > leaves.
Bioconcentration factor (BCF) and
Translocation factor (TF):
The Bioconcentration Factor (BCF) of metals was
used to determine the quantity of heavy metals that
is absorbed by the plant from the soil. This is an
index of the ability of the plant to accumulate a
particular metal with respect to its concentration in
the soil (Ghosh and Singh, 2005a) and is calculated
using the formula:
Metal concentration in plant tissue
BCF = _________________________________
Initial concentration of metal in
substrate (soil). The higher the BCF value the more suitable is the
plant for phytoextraction (Blaylock et al., 1997). BCF
Values > 2 were regarded as high values. To
evaluate the potential of plants for phytoextraction
the translocation factor (TF) was used. This ratio is
an indication of the ability of the plant to
translocate metals from the roots to the aerial parts
of the plant (Marchiol et al., 2004). It is represented
by the ratio:
Metal concentration (stems + leaves)
TF = ___________________________
Metal concentration (roots)
Metals that are accumulated by plants and largely
stored in the roots of plants are indicated by TF
values < 1 with values > 1 indicating that the metals
are stored in the stems and leaves. Determination
of hyperaccumulator and excluder plant species is
based on strict criteria. A plant is classified as a
hyperaccumulator for heavy metal (s) when it meets
four criteria; (a) shoot/root quotient (level of heavy
metal in the shoot divide by level of heavy metal in
the root) > 1, (b) extraction coefficient (level of
heavy metal in the shoot divide by total level of
heavy metal in the soil) > 1; extraction coefficient
gives the proportion of total heavy metal in the soil
which is taken up by the plant shoot/aerial part of
the plant (Harrison and Chirgawi 1989, Rotkittikhun
et al. 2006), (c) higher levels of heavy metals of 10 –
500 times the levels in normal plants
(uncontaminated plants) according to Allen (1989)
(d) more than 1000g/g of copper, lead, nickel,
chromium; or more than 100g/g of cadmium or
more than 10000g/g of zinc (Shen and Liu 1998,
Ginocchio and Baker 2004, , Rotkittikhun et al.
2006). Furthermore, a plant which has high levels of
heavy metals in the roots but with shoot/root
quotients less than 1 is classified as a heavy metal
excluder (Boularbah et al. 2006). According to Baker
and Walker (1990) an indicator plant species is the
one of which the levels of heavy metals in the
tissues are similar to those in the surrounding
environment; soil.
The rate of metal translocation from the root to the
shoot may depend on metal concentration in the
root (Hardiman et al., 1984). The movement of the
heavy metal from the polluted sediments into the
roots of the plant and the ability to translocate the
metals from roots to aerial parts were assessed
correspondingly by means of Bioconcentration
Factor (BCF) and the Translocation Factor (TF).
Bioconcentration factor is an index of the ability of
plant to accumulate a particular metal with respect
to its concentration in the sediment (Ghosh and
Singh, 2005). Bioconcentration factor (BCF) was
calculated as a ratio of concentration of heavy metal
in plant roots to that of soil. Translocation factor is
the ratio of metal concentration in the shoots to the
roots. The ability of plants to tolerate and
accumulate heavy metals is useful for
phytoextraction and phytostabilization purpose
(Yoon
et al.,
2006). Plants with both
bioconcentration factors and translocation factors
greater than one (TF and BCF> 1) have the potential
to be used in phytoextraction. The higher the BCF
value higher the suitability of the plant for
phytoextraction (Blaylock et al., 1997). This ratio is
an indication of the ability of the plant to
translocate metals from the roots to the aerial parts
of the plant (Marchiol et al., 2004). Based on the
results bioconcentration factor and translocation
factor values were calculated. Bioconcentration
factor was calculated using soil lead and nickel
background concentrations. Lead and Nickel
backgrouned concentration was 9.47mg/kg and
8.43mg/kg respectively. Lead bioconcentration
factor was 7.1 and translocation factor was 0.14.
Nickel bioconcentration factor value was 2.44 and
translocation factor value was 1.31. Based on these
values the plant species was highly accumulated
these metals in the roots part, finally it was very
useful for phytostabilization.
4.0 Conclusion:
1. Heavymetals uptake by plants using
phytoremediation technology seems to be a
prosperous way to remediate heavymetals
contaminated environment. Phytoremediation is a
fast developing field, sustainable and inexpensive
process.
2. Fast growing plants with high biomass and good
metal uptake ability are needed. In most of the
contaminated sites hardy, tolerant, weed species
exist and phytoremediation through these and
other non-edible species can restrict the
contaminant from being introduced into the food
web.
3. In the present study Catharanthus roseus, a non
edible, shrub species aesthetically pleasent with
beautiful flowers. Finally it was concluded that the
plant species highly accumulated lead than nickel.
Based on the bioconcentration factor and translocation factor values the plant species was a
good accumulator of these two metals.
From the above information write the main points
1. Nickel accumulation in Catharanthus roseus plants increased over time, with the highest accumulation observed in the stem part after 20 days.
2. Accumulation of nickel continued to increase in the roots, stem, and leaves of the plants, with a significant difference in accumulation observed in the leaf part after 40 days.
3. By the 60th day, nickel accumulation had almost doubled compared to the 40th day, with high accumulation observed in all parts of the plant.
4. The order of nickel accumulation in the plant was roots > stem > leaves.
5. Bioconcentration Factor (BCF) and Translocation Factor (TF) were used to assess the plant's ability to accumulate and translocate heavy metals from the soil to the aerial parts of the plant.
6. A BCF value > 2 is considered high, indicating suitability for phytoextraction.
7. TF values < 1 indicate heavy metals are stored in the roots, while values > 1 indicate metals are stored in the stems and leaves.
8. Catharanthus roseus was found to be a good accumulator of lead and nickel, with high BCF and TF values.
9. The plant species showed potential for phytoremediation and phytostabilization of heavy metal-contaminated environments.