Microgreens, harvested within 7-21 days, are nutritionally dense and are rich sources of antioxidants, minerals, and vitamins required for body and mental health. However, poor germination, leading to poor establishment, seed-borne diseases, and high water consumption often limit microgreen production. Low-temperature plasma (LTP) is a partially ionized gas with unbound electrons, neutral particles, ions, reactive nitrogen and oxygen species, and ultraviolet light. LTP is emerging as a viable non-chemical tool for seed priming, improving crop productivity, and disinfecting seeds and foods, among other uses. Thus, LTP may address the concerns limiting microgreen production. The effects of LTP on imbibition, germination rate of germination, seedling biomass, and drought tolerance were assessed primarily using mustard greens and ten microgreen crops with or without Ar or He Plasma at different exposure times. The drought tolerance experiment induced drought stress using PEG 6000 at 0 (Control), 5, 10, and 15% at w/v. The treated or untreated seeds were placed in Petri dishes and later transplanted into pots containing soilless potting mix. The days to first seed germination, germination rate, seedling height, root length, seedling and root biomass were recorded. Ar and He LTP hastened seed germination and increased the total seed germination percentage over Control. Ar and He LTP enhanced seed germination by 12.7% and 5.6%, respectively. He LTP increased seedling length by 40% and doubled the seedling fresh biomass over the Control. Ar LTP at 30 s and He at 90 s increased the root length by nearly 17% and 71% over that of Control, respectively. In another study, seeds directly exposed to either LTP or plasma-activated water (PAW) showed a 36% increase in seed germination compared to Control. Plant height significantly increased by 98% in Ar30 seconds and 50% (all other treatments) compared to Control. Exposure of seeds directly to He and Ar plasma also increased seedling biomass. He30s, He 60s, He 90s, and Ar 90s significantly enhanced biomass by 250%, 200%, 215%, and 120%, respectively compared to Control. In another study, seeds of ten microgreen crops exposed to Ar LTP for 30 seconds or He LTP for 90 seconds significantly boosted imbibition and germination rates compared to untreated seeds within 24 hours of treatment. The study showed that Ar or He LTP could improve the drought tolerance of microgreens by shortening the crop growing cycle and increasing root length without compromising seedling biomass.
