durations (2, 4 and 14 h)) on plant growth and parameters of
oxidative stress. The data suggest that non-thermal exposure
to investigated RF EMFs, especially at 900 MHz, induced
oxidative stress in duckweed and might influence plant
growth. Observed responses depended
on the field frequency
as well as other exposure parameters like field strength,
modulation and exposure time (17; 18). Schmutz et al.
investigated the long-term effect of 2.45 GHz radiation on
trees spruce (
Picea abies (L.) Karst.) and beech (
Fagus
silvatica L.). EM radiation caused no visual symptoms of
damage. The only effect of microwave exposure was a
decrease of calcium and sulfur concentrations in beech leaves
with increasing power flux densities (15). Tafforeau et al.
studied the effects of 100 GHz EM radiation on flax (
Linum
usitatissimum L. var Ariane). A single 2 h exposure to 105
GHz at non-thermal levels induces meristem production with
kinetics similar to that induced by weak environmental
stimuli and irradiation from GSM telephone (16). Magone
used a
sensitive clone of Spirodela polyrhiza (L.) Schleiden
to study the effects of the Skrunda Radio Location Station in
Latvia (156–162 MHz, 5 days exposure). The vegetative
reproduction rate was accelerated in the first 20 days after the
end of exposure. The vegetative growth rate was lower in
plants just beginning formation. At 55 days, various
morphological and developmental abnormalities appeared.
Plants developed completely to daughter fronds under EMF
exposure had a shorter life-span and a fewer subsequent
daughters (11).
There still are not enough investigations and sufficient
explanation for the mechanisms of
observed biological
effects of radiofrequency EMF, particularly in the absence of
gross cell/tissue heating effects. Investigation of RF EMF
effects on enzymes would contribute to clarifying
mechanisms of effects of this radiation on organisms. Almost
all processes in a biological cell need enzymes to occur at
significant rates. Since enzymes
are selective for their
substrates and speed up only a few reactions from among
many possibilities, the set of enzymes made in a cell
determines which metabolic pathways occur in that cell.
Consequently, the network of metabolic pathways within
each cell depends on the set of functional enzymes that are
present.The limited number of studies on enzyme systems
has yielded mixed results.
Enzyme activity was increased,
decreased or did not altered depending on the exposure
parameters (frequency, modulation, exposure duration, SAR),
enzyme type and localization (1; 5; 4; 6; 13). Some autors
investigated antioxidant enzymes (7; 8; 12). The question of
whether the radiofrequency fields of cellular phones affect
oxidative stress and the antioxidase activities are of
considerable interest to biomagnetics and biochemistry.
The purpose of our study was to investigate the alterations
in enzyme activities in leaves
after exposure of plants
Plectranthus sp. to 900 MHz EMF and their dependence on
the time elapsed after exposure.
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