1021-4437/03/5002- $25.00 © 2003
Russian Journal of Plant Physiology, Vol. 50, No. 2, 2003, pp. 147–154. Translated from Fiziologiya Rastenii, Vol. 50, No. 2, 2003, pp. 165–173.
Original Russian Text Copyright © 2003 by Dukhovskis, Juknys, Brazaityte, Zukauskaite.
Recently an environmental pollution became a very
important external factor to which plants are not
adapted evolutionarily. The environmental pollution
strongly affects plant growth and development, as well
as the state of natural and agricultural phytocenoses at
the local, regional, and global scale. Acid rains, an
increased ozone concentration in the air layer near the
ground, a depletion of stratosphere ozone layer, inten-
siﬁcation of ultraviolet radiation, and global climate
warming are anthropogenic processes, which can
unpredictably affect the wildlife [1–4].
The increased role of anthropogenic factors in the
environmental pollution makes urgent the studies of
integrated effects of natural and anthropogenic factors
on living organisms. In addition to direct impact on
plants, pollutants were shown to narrow plant tolerance
limits, i.e., to reduce plant resistance against natural
factors (temperature, moisture, etc.). In addition, the
effects of one and the same concentration of the same
pollutant on plants may vary [5–7], depending on envi-
So far, the attention was centered on the effects of
pollutants or other stress factors on forests . How-
ever, at present, more attention is given to the effects of
environmental pollution on growth and productivity of
cultivated plants [1, 9, 10].
Although, due to international efforts, emission of
such pollutants as sulfur and nitrogen compounds has
been reduced during the last decades, the environmen-
tal acidiﬁcation remains one of the most urgent prob-
lems. In addition to its direct impact on plants, the
increase in soil acidity enhances the toxicity and uptake
of metals. Plants grown on acid soils (pH below 4.5)
accumulate several times more heavy metals than when
grown on neutral or alkaline soils .
In addition to abiotic factors, the analysis of the inte-
grated effect of various stressors on plants should also
include the analysis of biological variables, such as
plant stand density. Competitive stress increases with
increasing population density. Here, the competition is
regarded in the most general sense, as a negative impact
of some individuals on others by consuming the limited
natural resources (water, light, and mineral nutrients).
For example, in the forests growing in polluted environ-
ment, individual trees suppressed by competition were
more sensitive to pollutants .
Main focus of plant physiologists is on the speciﬁc
aspects of the impact of various stress factors. This pro-
vides for deeper insights into ongoing processes and
their mechanisms. However, in nature, plants are sub-
jected to the integrated effect of many natural and
anthropogenic factors. Therefore, from the ecological
point of view, the mechanisms of the effects of speciﬁc
stress factors and general consequences of the inte-
grated effect of these stress factors are both signiﬁcant.
Various stress factors were shown to produce some gen-
eral effects on plants . Studying such universal
mechanisms provides for both assessing the integrated
impact of various factors and forecasting the possible
consequences of this impact.
Plant Response to Integrated Impact of Natural
and Anthropogenic Stress Factors
P. Dukhovskis*, R. Juknys**, A. Brazaityte*, and I. Zukauskaite**
*Lithuanian Institute of Horticulture and Vegetable Growing, Babtai, Kaunas region, Lt-4335 Lithuania;
fax: (370-37) 555-176; e-mail: email@example.com
**Faculty of Natural Sciences, Vytautas Magnus University, Kaunas, Lithuania
Received October 24, 2001
—Responses of cultivated plants (
changes in growth characteristics, pigment and proline content, to an integrated impact of natural (temperature)
and anthropogenic (substrate acidity, population density, and heavy metals) stress factors were studied under
controlled environmental conditions. The experiments were carried out in a phytotron (tomato) and under lab-
oratory conditions (garden cress). The external stress factors produced a general suppression of growth and pig-
ment synthesis and differentially affected individual biological characteristics of the plants. Each of the stress
factors narrowed the interval of plant tolerance to other stress factors. Strong impact of one stress factor affected
plant homeostasis mechanisms by weakening plant response to other stress factors.
Key words: Lepidium sativum - Lycopersicon esculentum - acidity - plant stand density - temperature - heavy
metals - growth characteristics -pigments - proline
: MPC—maximum permissible concentration.