This document discusses phytoremediation and the use of various plants to remediate contaminated soils and water. It provides details on different phytoremediation processes including phytoextraction, rhizofiltration, and phytostabilization. It lists several plant species and their ability to remediate or hyperaccumulate different heavy metals and contaminants. These include Pteris vittata which can hyperaccumulate high levels of arsenic. The document also discusses using genetic engineering to modify plants' ability to uptake and tolerate heavy metals like cadmium. Finally, it provides an example of using the fern Azolla caroliniana and its associated arbuscular mycorrhizal fungi to remediate arsenic contaminated

1. Department of Plant molecular Biology
and Genetic Engineering
Prabhat Kumar Singh
Ph.D. scholar

2. Bioremediation
• Bioremediation can be defined as any process that
uses microorganisms, fungi, green plants or their
enzymes to return the natural environment altered
by contaminants to its original condition.
• Phytoremediation: The word's etymology comes
from the Greek <phyto> = plant, and Latin
<remedium> = restoring balance. Phytoremediation
consists in mitigating pollutant concentrations in
contaminated soils, water or air with plants able to
contain, degrade or eliminate metals, pesticides,
solvents, explosives, crude oil and its derivatives,
and various other contaminants, from the media that
contain them.

3. • Accumulator plants have the facility to concentrate
metals from soils that contain low as well as high
concentrations of metals. Plants that show exceptional
uptake of metals are known as hyperaccumulators.
• Accumulator plants have the facility to concentrate
metals from soils that contain low as well as high
concentrations of metals. Plants that show
exceptional uptake of metals are known as
hyperaccumulators.

4.  Phytoextraction – Reduction of metal concentration in the
soil by cultivating plants with a high capacity for metal
accumulation in the shoots;
 Rhizofiltration – Adsorption or precipitation of metals onto
roots or absorption by the roots of metal tolerant aquatic
plants;
 Phytostabilization – Immobilization of metals in soils by
adsorption onto roots or precipitation in the rhizosphere;
 Hydraulic control – Absorption of large amounts of water by
fast growing plants and thus prevent expansion of
contaminants into adjacent uncontaminated areas;
 Rhizodegradation – Decomposition of organic pollutants or
biotransformation of metals by rhizospheric organisms.
 Phyto volatilization – Detoxify soil metal contaminant by
bio-methylation processes.
 Phyto degradation – Uptake of contaminants and the
subsequent transformation, mineralization or metabilisation
by the plant itself through various internal enzymatic
reactions and metabolic processes (Prasad et al 2010).

5. The mercury contamination in environment is
primarily anthropogenic, more precisely, industrial
sources viz. coal thermal plant, iron and steel
industry, chloralkali plants, battery industry and so
on being the mail sources. Bioremediation by
microbes in mercury contaminated site detoxification
is quite established. Bacteria and several higher
plants have properties to make phytovolatilization of
mercury at contaminated sites.

6. Chromium is the chief heavy metal contaminant found in
the tannery effluent and chromite mine areas.
Phytoremediation appears to be one of the major thrust
areas in chromium contaminated land detoxification.
Selected chromium tolerant plants root zone in
association with VAM fungi, helps in hyperaccumulation
of chromium on site.
A number of tree species helps in phytoextraction of
chromium at contaminated sites.

7. Chromium is the chief heavy metal contaminant found in
the tannery effluent and chromite mine areas.
Phytoremediation appears to be one of the major thrust
areas in chromium contaminated land detoxification.
Selected chromium tolerant plants root zone in
association with VAM fungi, helps in hyperaccumulation
of chromium on site.
A number of tree species helps in phytoextraction of
chromium at contaminated sites.

8. Cyanide primarily found in waste
water of steel plants, gold mine
areas. Selected water plants like
water hyacinth (Eichhornia
crassipes) and bacteria are often
used for phytoremediation/
bioremediation purpose.

10. Sl.
No.
Plant’s name Common name Phytoremediation function
Agropyron repens Wheat grass Stabilization of lead in soil
Agropyron smithii Wheat grass Metal extraction (phyto extraction)
Agrostis castellana Beat grass Metal extraction (phyto extraction)
Agrostis tenuis Beat grass Metal extraction (phyto extraction)
Alyssum bertoloni -- Hyperaccumulation of metal (phyto
extraction)
Asabidopsis halleri -- Metal tolerance (phytoextraction)
Azolla pinnata Water fern Bioabsorption of toxic metals
(Rhizofiltration)
Azolla filculoides Water fern Bioabsorption of toxic metals
(Rhizofiltration)
Bacopa monnieri Water hyssop Metals accumulation
Brassica oleracea cauliflower Metals accumulation
(Phytoextraction)
Brasica napus Indian mustard Metals accumulation
(Phytoextraction)
Brassica juncea Rape Metals accumulation
(Phytoextraction)

11. Sl.
No.
Plant’s name Common name Phytoremediation function
Brassica campestris Cabbage Metals accumulation
(Phytoextraction)
Carex praegractlis Sedge Phytoirrigation
Elchhornia crussipes Water hyacinth Metal accumulation (Biosorption)
Hordeum brachyantherum -- Phytoiirrigation metal hyper
accumulation
Hydrocotyle umbellate Pannywort Biosorption of toxic metals
Hygrophila corymbosa -- Cadmium accumulation
Macademia neurophylla -- Metal hyperaccumulation
Pistia stratoites Water lettuce Metal hyperaccumulation
Pteris vittata / P. longifolia Brake fern As-hyperaccumulation
Salvinia molesta Kariba weed Metal accumulation
(Rhizofiltration)
Silene vulgaris Bladder champion Phytostabilization
Solidago hispida Hairy golden rod Phytostabilization
Streptanthus polygaloides -- Nickelhyperaccumulation
Vallisnaria spiralis Eel grass Metal hyperaccumulation
Vetiveria zizanordes Vetiver grass Metal hyperaccumulation
contd…
Source: Glass 1988, McGutcheon and Schnoor 2003, Prasad 2004, 2007, 2012, Prasad and Strzalka, 2002.

12. Genetic engineering modifications of the physiological and molecular mechanism of plants,
cadmium uptake and tolerance have also been successfully achieved and these show promose
in opening new avenues for enhancing the overall efficiency of cadmium phytoremediation
(Eapen and D’souza, 2005). The possibilities for genetic engineering plants for
phytoremediation is shown in the Fig.
Fig. : Possibilities for genetic engineering in phytoremediation

13. A number of genetically modified (transgenic) plants
have been generated and tested in recent studies
and they have demonstrated the merits of genetic
engineering in enhancing the tolerance, uptake and
/or bioaccumulation of Cadmium. Wojas et al. (2009)
have demonstrated in a study first of its kind that the
hetergenous expression of Arabidopsis MRP7 in
tobacco (Nicotiana tabacum var. xanthi L.) could
modify cadmium accumulation, distribution and
tolerance.

14. Sources: Brown H.J.M. (1966), H eevit E.J. and Smith, T.A. (1975)
Al Club moss; Hydrangea sp., tea plants
As Brown algae, fern like Pteris vittata
B Brown algae, Plumbaginaceae
Ba Rhizopods, Brazil nut
Cu Caryophyllaceae
F Dichopetalum cymosum
Li Thallictrum sp., Cissium Sp.
Mn Ferns, Digitalis purpurea
Mo Papilionaceae
Ni Alyssium sp., Hybanthus floridundus
Se Cruciferae, Astragalus racemosus
Sr Brown algae
V Amonita sp. Brown algae
Zn Thlaspi calaminare

16. Pteris vittata:
a highly efficient accumulator of arsenic

17. Common chemicals
 TCE(Trichlorethylene)- is a solvent that has
been widley used as a spot remover in
the dry cleaning industry for degreasing
engine turbines as an ingredient for
paints and cosmetics. Also it has been
used as a anesthetic.
 Lead
 Heavy metals
 Toxins

18. Process

19. arbuscular mycorrhizae
Agely et al. (2005)
found that AM fungi
tolerated arsenic
amendments,
increased frond dry
mass at the highest
arsenic application
rate, and increased
arsenic uptake
across a range of
phosphorous
levels.

20. Azolla caroliniana

21. Azolla caroliniana

22. Why phytoremediation? Why ferns?
Phytoremediation is a
cost effective, low
technology treatment
that uses plants to
decrease the
concentrations of toxic
materials in soils and
waters.
The ferns that
hyperaccumulate
arsenic are candidates
for phytoremediation as
they are fast growing,
can be harvested
several times a year and
are capable of removing
substantial amounts of
arsenic from the
surrounding soil.