Can you imagine clearing up polluted water bodies with aquatic
plants? Soon, it might be a reality as scientists of the University
College in the city have found plants that have the capability to absorb
heavy metals from water bodies and render them harmless.

With
their focus back on nature now, many science labs had been looking
around for organisms, from bacteria to plants, that can absorb the
pollutants flushed into the environment, be it water or land. But even
microbes were often found to be at a loss on how to deal with heavy
metals such as cadmium and lead. That is when the research teams turned
to plants.

Among the many such research groups in the city
focusing on this area, the one at the Department of Botany, University
College, has managed to zero in on several plants that have the ability
to remove toxic substances from soil and water and thus detoxify them,
in a process scientifically known as ‘phytoremediation.’

The
University College group comprising Princymol Stephen, Devi Chinmayee M,
Mary Sheeba A, Swapna T S and Mini I  recently found that the aquatic
plant ‘Pistia stratiotes’ not only has a high tolerance level for toxic
heavy metals but that it can also be used quite effectively in
phytoremediation.

The little pond inside the University College
was where Pistia was grown. It was later exposed to heavy
metal-contaminated water in the lab for as long as ten whole days, after
which the researchers analysed the enzymes of the plant to see how well
it tolerated the stress.

 ’Only stress-tolerant plants can be
effective in dealing with the heavy metals. We found the antioxidant
defence mechanism in Pistia to be quite good,’’ said Swapna, who along
with Mini, leads the phytoremediation studies at the Botany Department.

They
found that Pistia could easily absorb copper, lead and cadmium from the
surrounding water. ‘’It either nullifies these toxins or keeps them
away in small bag-like structures called vacuoles, where they are
rendered harmless. When the plant dies, some of the metals may return to
the environment. Complete detoxification happens rarely, but we can
bring down the levels of pollution,’’ said Swapna.

The other side
of the story is that some of the commonly used leafy vegetables may have
this accumulative bioremediation properties and that would be bad news
for those who consume these vegetables regularly. A wild relative of our
‘Cheera’, the ‘mullan cheera’, was found to have a very high
bioconcentration factor and it accumulates copper and lead much above
the toxic limits.

‘’So, if you are consuming ‘mullan cheera’, you
really need to know where it comes from. If coming from polluted sites,
it may be harmful since the plant accumulates and translocates metals to
the leaves,’’ said Swapna.

Since the ‘mullan cheera’ showed such
high values for bioaccumulation, the research group is also studying the
common green ‘cheera’, scientifically known as Amaranthus viridis. The
group is also studying several aquatic plants such as Lemma, Spirodela,
Hydrilla and Salvinia if they can clear up toxic matter from water
bodies.

 Perhaps, our water bodies are already heaving a sigh of relief.