ISSN 10214437, Russian Journal of Plant Physiology, 2010, Vol. 57, No. 4, pp. 501–508. © Pleiades Publishing, Ltd., 2010.
Published in Russian in Fiziologiya Rastenii, 2010, Vol. 57, No.4, pp. 538–546.
Cadmium (Cd) is a highly toxic trace element,
which enters the environment mainly from industrial
processes and phosphate fertilizers. It can reach high
levels in agricultural soils and is easily assimilated by
plants. At present, more than 400 species of hyperac
cumulators have been documented in the world.
Noticeably, some Cd hyperaccumulators such as
successfully screened one after the other, and Indian
mustard has been used for the phytoremediation of
lead and Cd.
Evidence has been reported suggesting that Cd tox
icity takes the form of oxidative stress caused by the
stimulation of free oxygen radical production  and
by the modified activity of various antioxidant
enzymes. Under severe stress conditions, however, the
antioxidant capacity may not be sufficient to minimize
the harmful effect of oxidative injury. Survival under
This text was submitted by the authors in English.
stressful conditions depends on the plant ability to
perceive the stimulus, generate and transmit signals,
and induce biochemical changes, which adjust the
Superoxide dismutase (SOD) dismutates superox
ide radicals to hydrogen peroxide and
in a reaction
that is spontaneous and extremely rapid, thus protect
ing the cells from damage by superoxide radical reac
tion products . Peroxidase (POD) can participate in
lignin biosynthesis and conversion of
Regulation of antioxidant enzymes can provide plants
with an additional protective ability against oxidative
stress . Malondialdehyde (MDA) is usually consid
ered as an indicator of the degree of plant oxidative
stress and the structural integrity of plant membranes,
when plants are subjected to low temperatures .
Photosynthesis and respiration can further alter dis
solved inorganic carbon concentrations and its isoto
pic composition, and Krantev et al.  reported that,
although salicylic acid has a beneficial effect on pho
tosynthesis in the case of Cd stress, the compound
itself stressed the plants.
Glutathione (GSH) is associated with stress resis
tance. It is an important antioxidant in the cellular
milieu and is responsible for the maintenance of the
antioxidant machinery of the cells intact under stress.
The involvement of phytochelatins (PCs) in metal
Phytoextraction of Cadmium and Physiological Changes
as a Novel Cadmium Hyperaccumulator
, P. Zhou
, L. Mao
, W. J. Shi
, and Y. E. Zhi
School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai, 200240, China;
School of Agriculture and Biology, Shanghai Jiaotong University, Shanghai, 200240, China
Key Laboratory of Urban Agriculture (South), Ministry of Agriculture, Shanghai 200240;
fax: 8602134202901; email: firstname.lastname@example.org
Received October 15, 2008
—It is still difficult to fully understand the physiological, biochemical, and molecular mechanisms
involved in metal hyperaccumulation and how plants adjust to an adverse environment.
a novel Cdhyperaccumulator, which antioxidant defense and photosynthetic CO
fixation were investigated
in this study. The results showed that the elevated heavy metal concentration, inhibiting
was accompanied by a decrease in the photosynthetic CO
fixation. The presence of heavy metal in soil led
to disturbances in the antioxidant responses, especially in superoxide dismutase, malondialdehyde, phytoch
elatins, and total acidsoluble thiols, which indices in
were significantly correlated with the elevated
heavy metal concentration. Whereas peroxidase activity in
showed a slight difference and irregular
change, reduced glutathione significantly decreased with increasing culturing time and elevated Cd concen
tration. Thus, the manipulation of antioxidant enzyme activities increases tolerance, thereby potentially
increasing the uptake capacity of an organism.
Key word: Solanum nigrum,
antioxidant enzymes, cadmium, photosynthesis
: BF—bioaccumulation factor; DTPA—diethylen
etriaminepentaacetic acid; GSH—glutathione reduced;
GSSG—glutathione oxidized; NBT—nitroblue tetrazolium
chloride; PCs—phytochelatins; POD—peroxidase; SOD—
superoxide dismutase; TAST—total acidsoluble thiols; TBA—
thiobarbituric acid; TF—transfer factor.