We give preliminary results on the breakdown and low current limit of volt-ampere characteristics of simple parallel plate non-equilibrium dc discharges at standard (centimetre size) and micro-discharge conditions. Experiments with micro-discharges are reported attempting to establish the maintenance of E/N, pd and j/p 2 scalings at small dimensions down to 20 µm. It was found that it may not be possible to obtain properly the left-hand side of the Paschen curve. The possible causes are numerous but we believe that it is possible that long path prevention techniques do not work at high pressures. Nevertheless, the standard scaling laws seem to be maintained down to these dimensions which are consistent with simulations that predict violation of scaling below 10 µm. Volt-ampere characteristics are also presented and compared with those of the standard size discharges.

In this work we present results of two significantly different types of plasma treatment on Paulownia tomentosa Steud. seeds. In the first type, seeds were directly treated in low‐pressure plasma and then imbibed with distilled water. In the second type, an atmospheric pressure plasma was used for obtaining plasma activated water (PAW) which is then used for imbibition of seeds. The CAT activity and protein content is evaluated during 4 d following the imbibition process, i.e., immediately after the phytochrome activation and in the 3 subsequent days. Comparison of results of treated seeds to the control group allows to correlate the enzyme activity and protein content during the initial stages of germination with plasma treatment types and treatment conditions.

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We discuss the effect of electrode shape on Paschen curves and our ability to seal off microdischarges to prevent long path breakdown. It was found that for structured electrodes at high pressures and small gaps, the left-hand side of the Paschen curve is relatively flat, extending the minimum to lower pd values. At high pd values the curves are almost identical to those at standard pressures/gaps and the discharge runs between the top plane of the cathode and the anode. For intermediate pd values the higher electric field at the edge attracts most of the current and the discharge extends along the side wall maintaining the same low breakdown voltage. When the length of the discharge reaches the longest path the voltage starts a rapid increase. We have selected the dimension of the segmented electrode so as to have the same losses to the walls that block or allow the long path breakdown, thus being able to represent situations when the Paschen curve may be properly determined. In general, however, this shows that recording of the left-hand side for open structures (without enclosure by a dielectric) is impossible and conclusions about secondary emission should be focused on the well-defined conditions.