ISSN 10214437, Russian Journal of Plant Physiology, 2012, Vol. 59, No. 6, pp. 748–756. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © N.V. Shalygo, I.N. Domanskaya, M.S. Radyuk, R.A. Shcherbakov, I.A. Dremuk, 2012, published in Fiziologiya Rastenii, 2012, Vol. 59, No. 6, pp. 746–755.
As a result of heavy and prolonged rainfall, as well
as in the lowlands and at the shallow ground water, soil
is oversaturated with water, leading to plant flooding.
In this case, the content of oxygen in the roots
decreases (hypoxia), which is related to its low diffu
sion rate and limited solubility in water . Permanent
or temporary soil waterlogging is characteristic of
many regions of the Earth, including northwestern
regions of Russia and Belarus.
Higher plants are sensitive to oxygen shortage
because they are aerobic organisms and require a con
tinuous uptake of oxygen from the environment for
their normal life. However, there are some plants
capable of growth not only in oxygendepleted
medium but also in its complete absence. In the first
turn, they are hydro and hygrophytes, which acquired
a capability of growth on waterlogged and even
flooded soils during evolution. Rice is one of such cul
tivated plants; as it is known, rice is grown predomi
nantly on flooded soils. A capability of organisms to
tolerate temporary oxygen deficit is widely spread in
the Nature. Among cultivated plants, winter crops (in
particular barley, wheat, or rye) are most often turned
out to be under such conditions. In most plants, oxy
gen shortage retards growth, which is, for example,
characteristic of barley. In plants tolerant to hypoxia,
shoots can be lengthened whereas root growth is usu
ally retarded . According to numerous studies, such
plants have some morphological and biochemical
adaptive traits concerning mainly the respiratory and
energetic cell metabolism [3, 4].
Some plants can compensate oxygen shortage in
medium surrounding roots by its transport from
shoots. Such strategy of anaerobiosis avoidance due to
longdistance oxygen transport through aerenchyma
is called as the apparent tolerance .
When hypoxia is long, oxygen deficit becomes so
strong that plants should adapt to functioning in oxy
genfree environment on the level of metabolism .
Therefore, along with the apparent tolerance, plants
Accumulation of Hydrogen Peroxide and Functioning
of Defense System in Overwatered Barley Seedlings
N. V. Shalygo, I. N. Domanskaya, M. S. Radyuk, R. A. Shcherbakov, and I. A. Dremuk
Institute of Biophysics and Cell Engineering, National Academy of Sciences of Belarus,
Akademicheskaya ul. 27, Minsk, 220072 Belarus;
Received October 25, 2011
—The effects of overwatering (flooding) on the oxidative potential, the level of lowmolecular
weight antioxidants, the content of stress proteins, and activities of antioxidant enzymes in green barley (
L.) seedlings were studied. Overwatering retarded barley seedling growth and induced hydrogen
peroxide accumulation, a decrease in the total ascorbate content and an increase in the content of reduced
glutathione (GSH), but it did not affect the content of oxidized glutathione (GSSG). After the cessation of
stress factor action (poststress period), the content of hydrogen peroxide declined to the initial level, the
content of ascorbate reduced still stronger, whereas the content of GSH continued to rise. Under flooding
conditions, activities of glutathione reductase (GR) and superoxide dismutase (SOD) increased. After the
cessation of stress factor action, activities of these enzymes decreased but remained at rather high levels as
compared with control. Activity of catalase (CAT) reduced during stress, whereas activity of ascorbate per
oxidase (APX) was not essentially changed. In the poststress period, CAT activity remained to be low; in
contrast, APX activity increased. Barley seedling flooding induced the synthesis of stress proteins, HSP70 and
dehydrins (DH). In the poststress period, the content of stress proteins decreased; however, the content of
DH in experimental leaves remained rather high. The results obtained indicate that barley defense system
manifested a complex response to overwatering, which may be related to the oxygen shortage under stress
conditions and sharp metabolism activation at reaeration in the poststress period.
Keywords: Hordeum vulgare
, overwatering, flooding, antioxidants, antioxidant enzymes, stress proteins,
: APX—ascorbate peroxidase; CAT—catalase,
DH—dehydrins, GR—glutathione reductase; GSH—reduced
glutathione; GSSG—oxidized glutathione; HSP—heatshock
proteins; NBT—nitro blue tetrazolium; PC—phenolic com
pounds; SOD—superoxide dismutase.