Effect of plasma-activated water on peanut seed germination and vegetative growth in a hydroponic system

Peanut sprouts have recently been reported to be rich in some nutrients, including vitamin C, resveratrol, antioxidants, and folate, and are consumed as functional food. However, the effect of indirect plasma treatment, such as plasma-activated water (PAW), on the germination rate and growth of peanut remains largely unknown. Here, we evaluated the effect of PAW produced using a surface dielectric barrier discharge (SDBD) device on germination and vegetative growth in peanut. SDBD-generated PAW had significantly higher nitrate content than tap water (TW). Compared with the TW group, PAW treatment increased the germination rate of peanut seeds by more than twofolds at 3 days after planting; however, there was no significant difference in final germination rate between the PAW and TW groups at 7 days after seeding. In addition, PAW treatment significantly improved biomass-related morphological traits in peanut sprout compared with TW treatment. At the cellular level, PAW treatment increased cell size in the hypocotyl in both the horizontal (115%) and longitudinal (209%) directions, resulting in increased hypocotyl growth. Moreover, histological analysis showed that PAW treatment significantly enlarged parenchyma cell size in hypocotyl pith tissue but did not affect cell number. Overall, these results showed that PAW treatment improved seed germination and growth by enlarging parenchyma and epidermal cell size in hypocotyl, resulting in increased biomass in peanut sprouts. QRT–PCR results showed that auxin response and growth-related genes ( AhARF5, AhIAA13, SAUR32, AhGI-13, AhGI-75, AhCUC3-12, and AhCUC3-65 ) were upregulated in the PAW treated condition at 6 days compared to the TW treated sprouts.