1021-4437/05/5202- © 2005
Russian Journal of Plant Physiology, Vol. 52, No. 2, 2005, pp. 213–219. From Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 243–249.
Original English Text Copyright © 2005 by Ivanov, Alexieva, Karanov.
Under normal environmental conditions, the plants
are exposed to a complex of stress factors which could
be formally divided into two major groups, i.e., natural
(for example, extreme temperatures, water shortage, or
logging) and anthropogenic (pesticides, heavy metals,
air pollutants and an increased UV-radiation) . Now-
adays, the combination of natural and anthropogenic
stressors is a worldwide phenomenon.
Theoretically, two main effects of unfavorable con-
ditions are possible, namely plant death or adaptation to
the new environmental situation. Some cases are
known when a weak stress factor enhances the plant
adapting capacity to a subsequent stress. A typical
example is a higher frost resistance after a short expo-
sure to low positive temperatures or water shortage .
On the other hand, the combination of acid rain with
high temperatures appears to be highly detrimental and
provoked the death of entire forests .
The presence of high levels of both water and soil
pollutants is now a typical situation in most regions.
The persistence of most herbicides in the soil varies
from several weeks to months (and even years).
Although each herbicide is applied for a particular
crop–weed situation at limited rate, area, and time
period, during the following months some residual
amounts of the herbicide are spread usually by rains
and underground water over larger areas and contact
with other crop plants and ecosystems. Such herbicide
spreading cannot be easily followed, and at low con-
centrations these compounds undoubtedly reach those
plant and animal organisms, at which they were not
aimed initially. In these cases, they combine their inﬂu-
ence with the effects exerted by unfavorable environ-
mental conditions, both natural and anthropogenic.
Moreover, in crop ﬁelds some additive effects take
place due to the subsequent application of herbicides at
Atrazine frequently contaminates soil, groundwater,
rivers, and ponds . The highest detected residual
amounts reach 1mg/kg soil . Usually, in the agricul-
tural areas this herbicide can be detected in 1–100
per kg soil or liter water [3, 5–7]. On the other hand, it
was reported that in some plants the same atrazine con-
centrations exhibit cytokinin-like properties .
The aim of our experiments was to ﬁnd how some
trace amounts of atrazine could affect the adaptive
capacity of the
plants to subse-
quent acute stress factors. The severe stress was
induced by the same herbicide but applied at the lethal
dose normally recommended for agricultural practice.
Since the primary phytotoxicity of atrazine is due
mainly to the overgeneration of active oxygen species
(AOS), we considered the amounts of produced hydro-
gen peroxide and the level of lipid peroxidation mea-
sured in malondialdehyde (MDA) equivalents as crite-
ria for the development of free-radical chain reactions
causing an oxidative damage to plant tissues.
Cumulative Effect of Low and High Atrazine Concentrations
S. V. Ivanov, V. S. Alexieva, and E. N. Karanov
Acad. M. Popov Institute of Plant Physiology, Bulgarian Academy of Sciences,
ul. Acad. G. Bonchev 21, Soﬁa, 1113 Bulgaria;
Received September 12, 2004
—Atrazine belongs to the widely used herbicides blocking the electron transport chain in chloroplasts,
thus resulting in the generation of active oxygen species. In the present work, we demonstrated that, at low con-
centrations mimicking residual amounts, atrazine enhanced the susceptibility of
plants to further
treatments with the same herbicide applied at the recommended ﬁeld rate.
treated three times (at ﬁve-day intervals) with 1
M atrazine. Five days after the last treatment, the plants were
sprayed with 5 mM atrazine. Atrazine increased the levels of lipid peroxidation products, hydrogen peroxide,
and ion leakage, and caused changes in the activities of antioxidant enzymes, such as superoxide dismutase,
guaiacol peroxidase, and catalase.
Key words: Arabidopsis thaliana - antioxidant enzymes - residual amounts of atrazine - oxidative stress
: AOS—active oxygen species; MDA—malondial-
dehyde; NBT—nitro blue tetrazolium; PSII—photosystem II;
This article was submitted by the authors in English.