Alterations in Enzyme Activities in Leaves after Exposure of Plectranthus Sp. Plants to 900 mhz elec
tải về 0.92 Mb. Chế độ xem pdf
|
ELECTROMAGNETICFIELDSandELF
| Introduction
Accelerated and widespread use of different communication systems and modern electronic equipment has increased exposure to radio frequency electromagnetic fields (RF EMF) and has raised serious concerns about the biological and health-related effects of RF radiation. Numerous studies have documented various biological effects of RF radiation. Most of them concern health, brain and DNA effects. However, most of these findings derived from epidemiological, animal and in vitro studies while only a few investigated effects of RF radiation on plants. Assessment of the RF EMF impact on plants is of great importance because plants have an important role in the living world as main primary producers of organic compounds and oxygen. Plants are continuously exposed to various environmental stresses and display a wide spectrum of developmental and biochemical responses contributing to stress adaptation. Their physiological responses can be evoked by a great variety of external stimuli, including mobile phone radiation. Some authors investigated responses of tomato plants (Lycopersicon esculentum Mill. VFN8) to exposure to low level 900 MHz EMF for 10 min and provide evidence that they perceive and respond to EMF as an injurious treatment (wound). High frequency EMF is an environmental stimulus that affects gene expression, transcription, translation and calcium and energy charge in tomato plants (2; 14; 19). Tkalec et al. investigated the effects of exposure of the duckweed Lemna minor to RF EMFs (400 MHz, 900 MHz and 1.9 GHz, different electric field strengths and exposure BIOTECHNOL. & BIOTECHNOL. EQ. 23/2009/2 XI ANNIVERSARY SCIENTIFIC CONFERENCE SPECIAL EDITION/ONLINE 120 YEARS OF ACADEMIC EDUCATION IN BIOLOGY 45 YEARS FACULTY OF BIOLOGY 611 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. tải về 0.92 Mb. Chia sẻ với bạn bè của bạn:
|