ISSN 10214437, Russian Journal of Plant Physiology, 2012, Vol. 59, No. 1, pp. 50–58. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © Yu.V. Ivanov, Yu.V. Savochkin, Vl.V. Kuznetsov, 2012, published in Fiziologiya Rastenii, 2012, Vol. 59, No. 1, pp. 57–66.
Like other essential elements, zinc microamounts
are vitally important for plant development, whereas
zinc high concentrations are toxic and can lead to the
organism death. Zinc is the only micronutrient
involved in all currently known enzyme classes . It
fulfills an important structural function in transcrip
tion factors; it is a cofactor of RNA polymerase, main
tains the integrity of ribosomes , and plays an
important role in the control of the cell redox potential
. For most plant species, the content of Zn in
aboveground organs is 15–50
g/g dry wt; the exceed
ing of this concentration is toxic for plants .
The negative impact of high zinc concentrations on
the vegetation is a major concern of ecologists and
plant physiologists in connection with the intense pol
lution with the metal of agricultural and forest lands.
Contamination of large areas with zinc results from
human activities related to utilization of household
wastes, irrigation of dry lands with water mixed with
industrial effluents, processing of ore production
waste . The availability of zinc to plants is closely
correlates with the level of soil acidity, increasing sig
nificantly with decreasing pH of the soil solution. At
these conditions, zinc is readily absorbed by plants in
amounts greater than their natural need in it .
Plants exposed to excess zinc concentrations man
ifest symptoms similar to those appearing after action
of other heavy metals.
Among nonspecific signs of plant damaging by
heavy metals are, primarily, disturbance in growth and
development of the root system, the reduction in the
biomass of aboveground organs, the appearance of
chlorosis in young leaves, the development of defi
ciency of phosphorus, iron, magnesium, and other
essential elements due to disturbance of their absorp
tion, transport, and utilization[ 7].
A common negative biochemical effect of heavy
metal high concentrations, zinc in particular, is ROS
generation and oxidative stress development .
Among ROS, especially dangerous are hydroxyl radi
), singlet oxygen (
), superoxide radical
and hydrogen peroxide (
with various organic molecules within the cell, ROS
can induce irreversible disturbances in the functioning
of macromolecules, membranes, metabolic processes,
Scots Pine as a Model Plant for Studying the Mechanisms
of Conifers Adaptation to Heavy Metal Action: 2. Functioning
of Antioxidant Enzymes in Pine Seedlings under Chronic Zinc Action
Yu. V. Ivanov, Yu. V. Savochkin, and Vl. V. Kuznetsov
Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya ul. 35, Moscow, 127276 Russia;
fax: 7 (499) 9778018; email: firstname.lastname@example.org
Received March 14, 2011
—Functioning of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), ascorbate
peroxidase (APO), and guaiacol peroxidases (GPO)) and lowmolecular organic ROS scavengers (proline
and phenolic compounds) in various organs (roots, cotyledons, stem, and needle) of 6weekold seedlings of
L.) developing in the chronic presence of ZnSO
(50, 100, and 150
M). Pine seedlings
were grown in water culture in the climatecontrolled chamber at an irradiance of 37.6 W/m
with a 16h
photoperiod, an air temperature of 23 ± 1/15 ± 1
C (day/night), and a relative humidity of 55/70%
(day/night). Endogenous Zn content was a key factor determining SOD activity decomposing superoxide
. Hydrogen peroxide produced is efficiently destroyed by CAT and also by APO and GPO.
At the same time, the content of proline increased (especially at 150
), but the content of phenolic
compounds remained unchanged. All these processes help to maintain stable intracellular levels of
at elevated zinc concentrations and to prevent generation of hydroxyl radical and development of oxi
Keywords: Pinus sylvestris
, zinc, oxidative stress, antioxidant enzymes, proline, phenolic compounds.
: APO—ascorbate peroxidase; CAT—catalase;
GPO—guaiacol peroxidases; PO—peroxidase; SOD—superox