Recent Progress of Non-thermal Atmospheric Pressure Plasma for Seed Germination and Plant Development: Current Scenario and Future Landscape

Seed germination is a complex physiological process initiated by water uptake and results in the emergence of radicles and plumules. Because water uptake is a prerequisite for germination, the presence of a hydrophobic or water-impermeable seed coat can limit the process of germination. Therefore, researchers are eager to modify the seed coat surface to facilitate germination. Among the various factors identified thus far, plasma treatment is emerging as one of the most efficient methods to promote seed germination. A growing body of evidence suggests that plasma treatment of seeds can increase the hydrophilicity and oxygen permeability of seed coats to promote the process of germination. Furthermore, pretreatment of seeds with various reactive oxygen- and nitrogen-enriched plasma-activated water has been shown to induce hormonal changes in the seeds, which promote germination and subsequent plant growth. Plasma-treated seeds are now being examined in agricultural areas as an efficient pre-sowing therapy for regulating seed germination, with the added benefit of sterilizing endospores or fungi to a degree. However, the molecular mechanism underlying plasma-induced seed germination still needs to be better understood, and germination behavior needs to be clarified. Most of the results reported thus far demonstrate that plasma has a favorable influence on seed germination; however, in some instances, it remains unaltered or even decreases. In this review, we examined the effects of plasma for pre-showing treatments, such as sterilization, storage, seed shape variation, watering, and probable genetic and hormonal alterations that might improve plant productivity.