References

358 A.G. Volkov
called undersampling and results in aliasing. The maximum sample rate is
specified in samples per second, and not in hertz.
Ag/AgCl electrodes were prepared from Teflon-coated silver wire (A-M
Systems) according to the method of Ksenzhek and Volkov (1998). The
Ag/AgClelectrodeswereidentical;oneelectrodeisreferredtoasthereference
electrode, and the other as the working electrode. The reference
electrode(–)wasinsertedinthestemorrootofasoybean,whereasthe
working electrode (+) was inserted in the stem or a leaf of a soybean. The
potential difference between the working electrode and the reference electrodeisreferredtoasthevariationpotentialintheplant.Themechanism
of generation of a variation potential is not clear. Variation potentials measured
in green plants, trees, and fruits typically have amplitudes from 20
to 140 mV.
24.5
Light-Induced Electrophysiological Signaling in Plants
The soybean was irradiated in direction A shown in Fig. 24.1 with white
light in a Faraday cage for 2 days with a 12 h : 12 h light-to-dark photoperiod
prior to conducting the experiments. Action potentials are not generated
when the lights are turned off and on (Fig. 24.2).
After 1−2 min of irradiation, a change in the direction of irradiation
from direction A to direction B generates action potentials in soybean
Fig.24.2. Potential difference between two Ag/AgCl electrodes in the stem of soybean under
irradiation (on)andinthedark(off ).Thedistancebetweentheelectrodeswas5cm.Thesoil
was preliminarily treated with water every day. The volume of soil was 0.5 L. The frequency
of scanning was 50,000 samples/s