Modification of seed germination performance through cold plasma chemistry technology

This study was conducted to determine if an alternate seed treatment approach based on plasma chemistry would offer a more viable alternative over traditional seed coating technologies. Seed germination characteristics were modified in five agricultural species by coating the surface of the seeds with macromolecules from a cold plasma process using a rotating plasma reactor. The source gas entering the plasma chamber during the reaction process determined the type of coating, and coatings were typically much less than 5.0 micrometer in thickness. To delay germination we utilized two different hydrophobic source gases, carbon tetrafluoride (CF4) or octadecafluorodecalin (ODFD). Seeds of radish (Raphanus sativus) and two pea cultivars (Pisum sativum cv. Little Marvel, P. sativum cv. Alaska) treated with CF4, resulted in a significant delay in germination compared with untreated controls. Similarly, plasma treatment with ODFD significantly delayed germination in soybean [Glycine max (L.) Merr.], corn (Zea mays L.), and bean (Phaseolus vulgaris L.) seeds. The degree of delay was dependent on the amount of coating applied, with an increased thickness of coating resulting in a greater delay in germination. To enhance germination we treated seeds with cyclohexane, or with a gas such as aniline or hydrazine. Seeds treated with cyclohexane resulted in a significant acceleration in germination percentage for soybean but not corn seeds, while hydrazine-treated corn seed showed a small acceleration over control seed. However, both aniline-treated soybean and corn seed had a significant acceleration in germination percentage. Tests of water uptake determined that the major mode of action of the plasma coatings was largely on the rate of imbibition. These results demonstrate a potentially important technique to modify seed germination characteristics in agricultural plant species.