Cadmium and heat (42°C, 2h) were used for positive controls.
Modulation type: CW
Exposure duration: continuous for 2 h
Modulation type: CW
Exposure duration: continuous for 2 hr or 4 hr
|Setup||Five plastic Petri dishes were placed in the GTEM cell in the same plane but perpendicular to the field. The area where plants were placed had the most uniform field distribution (±0.1 dB) as tested with an electric probe.|
|Sham exposure||A sham exposure was conducted.|
|Additional info||The temperature inside the GTEM cell and on the plant surface did not vary by more than ±0.1 °C.|
|electric field strength||10 V/m||-||measured||-||-|
|power density||0.3 W/m²||-||-||-||-|
|electric field strength||23 V/m||-||measured||-||-|
|power density||1.4 W/m²||-||-||-||-|
|electric field strength||41 V/m||-||measured||-||-|
|power density||4.2 W/m²||-||-||-||-|
|electric field strength||120 V/m||-||measured||-||-|
|power density||38.2 W/m²||-||-||-||-|
At 400 MHz, lipid peroxidation and hydrogen peroxide content were significantly enhanced in duckweed exposed to electromagnetic fields of 23 and 120 V/m, while other exposures did not have an effect.
Compared to the controls, catalase enzyme activity increased after most exposure treatments while pyrogallol and ascorbate peroxidase enzyme activities were not changed. Exceptions were reduced pyrogallol and ascorbate peroxidase enzyme activity after longer exposure at 23 V/m and increased pyrogallol enzyme activity after exposures at 10 and 120 V/m.
By contrast, at 900 MHz almost all exposure treatments significantly increased lipid peroxidation and hydrogen peroxide content but mostly decreased pyrogallol enzyme activity and did not affect catalase enzyme activity. Exceptions were exposures to a modulated electromagnetic field and to the electromagnetic field of 120 V/m which increased pyrogallol and catalase enzyme activity. At this frequency ascorbate peroxidase activity was significantly decreased after exposure at 10 V/m and longer exposure at 23 V/m but it increased after a shorter exposure at 23 V/m.
At both frequencies no differences in isoenzyme patterns of antioxidative enzymes or HSP70 level were found between control and exposed plants.
The data showed that non-thermal exposure under these experimental conditions induced oxidative stress in duckweed as well as unspecific stress responses, especially of antioxidative enzymes. However, the effects markedly depended on the electromagnetic field frequencies applied as well as on other exposure parameters (field strength, modulation and exposure time).