ISSN 1021-4437, Russian Journal of Plant Physiology, 2007, Vol. 54, No. 5, pp. 693–697. © Pleiades Publishing, Ltd., 2007.
Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 5, pp. 781–785.
The rare earth elements (REEs) include scandium,
yttrium, and 15 lanthanide elements, among which
cerium and lanthanum are the most abundant. They are
all nonessential to plants, nonbiodegradable and persist
in the environment .
Recent studies have shown that certain amounts of
REEs can enhance plant resistance to environmental
stresses, promote their growth and development, and
increase crop yields [2, 3]. REEs are now widely
applied in Chinese agriculture and also extensively
used as ﬁne chemicals, e.g., catalysts for emission con-
trol from motor vehicles . As a result, more and more
REEs are entering the soil and water environments.
Despite their low toxicity, the potential risk of the
uncontrolled release of REEs into the environment
should not be neglected. The introduction of REEs is
known to disturb the elemental balance in the environ-
ment and the biosphere . In the long run, REEs may
become a new type of pollution. Currently, consider-
able effort has been devoted to study the beneﬁcial
effects of REEs on plants [2, 3]. However, more atten-
tion has to be paid to the toxic effects of REEs on
plants. To our knowledge, this study is the ﬁrst report
on oxidative stress induced by La and Ce in aquatic
Aquatic plants are particularly sensitive to water
contamination because they are in direct contact with
the contaminants [6, 7] and absorb toxic metals from
the polluted water through both roots and leaves . In
the present study, the submerged plant
was chosen to investigate the toxic effects of REEs
on aquatic plants.
MATERIALS AND METHODS
Plant material, growth conditions, and treatments.
(L.f.) Royle plants were col-
lected from Suzhou, China and grown in a culture pool
for hydrophytes for one year. New plantlets (8–10 cm
in height) were separated from the mother plants,
washed in distilled water, and cultured in one-tenth
strength Hoagland solution in a controlled-environment
chamber at a 16-h photoperiod, an irradiance of
s), and at
After 6 weeks, the plants were transferred to ﬂasks
(6 plants per ﬂask) ﬁlled with 2 l of this nutrient solu-
tion, in which 0.2 mM
was replaced with
0.125 mM KCl to avoid the precipitation of
. Various concentrations (10, 30, 50, and
M) of La and Ce were prepared from
salts. Plants cultured in the nutrient solution
without La and Ce served as the controls. All solutions
were replaced with fresh solutions every two days. Tips
of 5-cm-long test plants were sampled after 10-day
experiments. The plant samples were washed thor-
Lanthanum- and Cerium-Induced Oxidative Stress
, G. X. Shi
, Q. S. Xu
, B. J. Xu
, and J. Zhao
College of Life Science, Shandong University of Technology, Zibo 255049, China;
College of Life Science, Nanjing Normal University, Nanjing 210097, China;
Received February 27, 2006
—Oxidative stress was induced in 10-day treated with lanthanum and cerium
plants. Low 10
M concentrations did not exert harmful effects. The plants treated with higher concentrations
content and lower chlorophyll and soluble protein contents as compared to control plants.
At the same time, malondialdehyde content rose with increasing concentrations of La and Ce. As La and Ce
concentrations increased, superoxide dismutase and catalase activities declined progressively, while peroxidase
activity increased. Proline content decreased slightly at 10
M La or Ce and then rose with higher concentra-
tions. The results indicated that La and Ce caused oxidative damage as evidenced by increased lipid peroxida-
tion and decreased chlorophyll and protein levels.
Key words: Hydrilla verticillata - cerium - lanthanum - oxidative stress
: CAT—catalase; MDA—malondialdehyde;
POD—peroxidase; REEs—rare earth elements; ROS—reactive
oxygen species; SOD—superoxide dismutase.
The text was submitted by the authors in English.