To study the effects of weak and extremely low frequency magnetic fields on the growth of spruce seedlings Picea abies that were exposed simultaneously to stress conditions.
The drought environmental stress conditions were simulated by watering the seedlings with polyethylene glycol at two different concentrations.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
repeated daily exposure, 12 h/day for 7 days or 12 h/day for 9 days; 2 days in water flasks and 7 days in Petri dishes
|
|
|
Exposure 2:
50 Hz
Exposure duration:
repeated daily exposure, 12 h/day for 7 days
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | repeated daily exposure, 12 h/day for 7 days or 12 h/day for 9 days; 2 days in water flasks and 7 days in Petri dishes |
| Exposure source | |
|---|---|
| Chamber | Experimental boxes maintained at about 21.5°C and the experiments were performed in the dark. |
| Setup | Petri dishes were placed at the center between the coils and exposed under normal conditions or under PEG stress (drought environment conditions) which was simulated by watering the seedlings with polyethylene glycol (PEG) at 88 g/L and 176 g/L. |
| Additional info | The axis of the coil was in east west direction in which the geomagnetic field was equal to zero. The coils were placed in a paper box shielded by grounded aluminum foil. The control group was exposed to equal composition and treatment, except that it was not exposed to magnetic field stimulation. The controls were performed by placing the seeds in the non-energized coils as well as placing them in control box which was located at a distance of 3.5 m from the coils. One control was preformed with PEG 88 g/L and the other two under normal conditions. In one experiment (PEG 176 g/L) subgroups were introduced, one group was exposed for 4 days and then placed into the control box for the remaining 3 days and the second group was first placed into the control box and then exposed to MF for the last 3 days. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 26 µT | unspecified | measured | - | - |
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | repeated daily exposure, 12 h/day for 7 days |
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 105 µT | unspecified | measured | - | - |
The data showed that a weak, sinusoidal magnetic field inhibited the germination and the growth of seedlings (under drought stress), whereas under normal conditions (without polyethylene glycol), the effects were either zero or stimulatory. When the seeds were soaked in water, the effects of magnetic fields were reversed (i.e. they were stimulatory). This supports some findings that biological systems under stress may demonstrate higher sensitivity to extremely low frequency electromagnetic fields.
The data show that the inhibition was greater at the higher concentration (176 g/l) of polyethylene glycol (at 105 µT), whereas the growth as well as the fresh weight did not show this dependence of concentration.
The authors suggest physiological windows, because the quality of responsiveness to magnetic fields may depend on the physiological state of organisms.
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