The vacuolar potential of characean cells subjected to electromagnetic radiation in the range 200–8,200 MHz

Abstract

Single giant cells of Chara braunii and Nitella flexilis were placed in a microstrip exposure apparatus and subjected to bursts of electromagnetic radiation (carrier frequencies from 200 to 8,200 MHz) at a nominal power level of 100 W/m². The vacuolar potential was monitored with a micropipette, and offsets as low as 1 μ V could be resolved in real time by suitable filtering and signal averaging; under these conditions, no offsets of the vacuolar potential were detected. At much higher power levels (corresponding to > 2 V rms between microstrip and ground plane), the slow hyperpolarizing ramp reported at lower frequencies could be seen but, because of insufficient power, could not be accurately measured. It appeared to decay beyond 500 MHz and to be absent at and above 950 MHz. To investigate reports that snail neurons irradiated for 1 h at 2,450 MHz and approximately 15.5 W/kg developed lowered membrane resistivities, Characean cells were exposed in the microstrip apparatus for 1 h at 2,450 MHz and 230 W/m²; their membrane resistivities were found to be lowered about 18.5%.