Wettability Increase in Plasma-Treated Agricultural Seeds and Its Relation to Germination Improvement

Abstract

The literature on plasma-stimulated modification of seed wettability and germination is reviewed and analyzed. The results reported by different authors are scattered, but there is a positive correlation between the change in the water contact angle and the germination improvement. There is hardly any correlation between the germination and the power density used for sustaining gaseous plasma. The wettability, on the other hand, exhibits optimal values at the power density of roughly 1 W cm−3, but the results differ significantly. In fact, a super hydrophilic surface finish was only reported at such moderate power densities. Both the wettability and germination increase with treatment time, but saturate at a certain level, depending on the discharge power. Unlike for most polymers, the hydrophobic recovery does not appear to be a considerable obstacle, so the plasma treatment may be performed well before sowing, which makes the technique applicable in agricultural practice. The scattering of results indicates that the commonly reported parameters such as the type and mode of discharge, the discharge power or power density, the type of gas and its pressure, the treatment time and the type of the seeds, are not decisive parameters governing wettability and germination. Based on the observations of the reviewing authors, conclusions and scientific challenges in this scientific niche are summarized.