HYBRID COLD PLASMA MEDIATED PLANT SEED GERMINATION ENHANCEMENT

Pathogen infestation can deteriorate the biological quality and nutritive value of crops and plant seeds. Atmospheric cold plasma has been extensively studied for biological and agricultural applications because the cold plasma is expected to interact with selective cell membranes at the submicron scale. It is, therefore, important to establish the impact of the cold plasma treatment on the wettability and germination characteristics of the seeds; however, few systems have been successfully translated into practical industrial systems. We describe a system to produce atmospheric hybrid cold-discharge plasma (HCP) based on the micro-corona discharge plasma in conjunction with a single dielectric barrier discharge (DBD). We applied the system to rice (Oryza sativaL.) seeds and investigated the modification of the seed surface and wetting properties and the effects on the germination percentage and seedling quality. The HCP can perform under atmospheric conditions at relatively low-temperature ∼27°C without destroying the seeds. We measured the water uptake and contact angle of a ∼2 μL water droplet on nontreated and treated seeds immediately after plasma application. The overall results showed that the wettability of the rice seed was improved significantly by the air-Ar plasma treatment, leading to increased water absorption. Germination testing was further carried out immediately after the plasma treatments in accordance with ISTA. The results demonstrate that HCP treatment also enhanced the germination percentage and seedling quality. The final germination percentage of the treated rice seeds was ∼98%, whereas that of the nontreated seeds was ∼90%. Moreover, the optical emission spectroscopy was performed to analyze the reactive species generated during plasma treatment. The result partially suggests that the Reactive Oxygen Species (ROS) generated by excited Ar species is an essential for surface modification and water imbibition enhancement. The SEM firmly indicated the nanoscale modification of the surface morphology and the decontamination of pathogenic fungi that commonly contaminate the surface of rice seeds. Therefore, the HCP can be considered as the potential approach for modifying seed characteristics. Not only does it increase the imbibition rate, but cold plasma also enhances the germination process, which could be advantageous for slow-to-germinate seeds. The hybrid nonthermal plasma is cost-effective and consumes relatively low power, making it applicable for the local and large - surface sterilization applications.