Effect of electrical stress produced by repetitive pulsed power on germination of naked barley seed between point-plane electrodes

This paper presents an experimental study on germination control for naked barley seed by using a repetitive pulsed power technique. Two kinds of tests, localized pulse electric field (PEF) treatment and dielectric barrier discharge (DBD) treatment, are carried out. In the first test, very short mono-polar pulses below 500 ns in width and below 5 kV in heights are applied to the seeds between point-plane electrodes with 500 pps repetition rate for 20 min. A fine stainless needle electrode is inserted into embryo region or endosperm region of the seed to clarify which region should be stressed by the localized PEF for the germination control. The germination rate of the seed after the PEF treatment is compared not only with that of the seed without any treatment (control) but also the seed with sham treatment, which means that the needle tip is inserted without voltage application. Results indicate that there is no effect of the PEF application into the endosperm region of the seed on the germination inhibition. On the other hand, the PEF application into the embryo region has an effect on the germination inhibition if the pulse width is long. In the second test, embryo region of the seed is exposed by the dielectric barrier discharges produced by the polarity-reversed voltage pulses with 100 ns in width. Evans Blue dyeing for the seeds is carried out to clarify the biological activity of the embryo cells. Embryo cell necrosis is caused by the 10 min discharge treatment. On the other hand, necrosis of the seed surface is not observed for the seed after the PEF treatment.