## 3 Applications of Cold Atmospheric Pressure Plasma
### Food Industry and Agriculture
The review papers of [PERSON] et al. focused on preharvest applications of CAPP in agriculture. These papers summarize laboratory experiments dealing with the effects of direct (DBD, APPJ) and indirect (plasma-activated water) treatments on the plant (e.g., wheat, corn, chili pepper, lentils, tomato, rice, etc.) growth and development. The CAPP generated RONS can alter the germination rate, plant morphology (shoot and root length, leaf area, etc. ), gene expression and biochemical processes (changes in hormones, amino acids, antioxidants, soluble sugar level, chlorophyll content, etc.). For example, higher antioxidant activity, growth hormones and metabolites led to early germination, improved germination percentage, elevated growth (root, shoot, leaves) and increased plant yield [110]. The paper of [PERSON] et al. described various CAPP treatments to keep the freshness and quality of agricultural products in the postharvest stage. For example, removing ethylene during storage and transportation (fruits and vegetables in storehouses, preservation boxes and transportation containers) is important because ethylene works as a plant hormone and it can induce fruit ripening and undesirable reactions (e.g., bitter flavors, yellowing of green leafy vegetables and increase of vulnerability to disease. Decomposition of ethylene is an oxidation process by atomic oxygen, which can be achieved using CAPP treatment (e.g., corona and DBD discharges) [111]. Plasma and plasma-treated water can also be utilized for controlling plant diseases (e.g., seed-borne, foliage, root and postharvest diseases) by inactivating pathogens (e.g., disinfection of seeds, fertilizer, water, soil) [109; 112; 113; 23]. Review paper of [PERSON] et al. concluded that plasma can also enhance seed germination (e.g., radish sprouts, wheat, sunflower, pea, tomato seeds). They described the possible mechanisms of plasma treatment in agriculture (increased gibberell level and decreased abscisic acid content, enhanced activity of catalase, superoxide dismutase and peroxidase, improved water absorption, elevated levels of proline, chlorophyll, polyphenols sugar and protein contents) [114]. Seed germination efficiency (speed, percentage) depends on the plasma source, plant species and moisture content. Plasma-induced physicochemical changes in the properties of the seed coat or surface (e.g., elevated hydrophilicity and water permeability) enhance water imbibition, which is essential for seed germination. [PERSON] et al. also discussed the beneficial effects of plasma treatment on seed germination, plant growth, and development. RONS can act as signaling molecules, which initiate a germination process and break the dormancy stage [108]. Another critical phase for plant development is the vegetative growth (it determines the overall crop productivity), which can be also regulated using plasma. As indicated by several studies, RONS have a positive effect on plant organs (shoots, roots, leaves and flowers) at different growth stages. Reactive species (H\({}_{2}\)O\({}_{2}\) and NO) may disturb redox homeostasis and trigger mild oxidative stress in plants [108]. Another application of CAPP technology is the enhancement of seedling growth, which depends on seed metabolism and external environmental factors. Even 1 min CAPP treatment significantly promoted the seedling growth (fresh weight and length increment) of Arabidopsis thaliana. The results of [PERSON] et al. suggested the plasma treatment accelerates the seedling abscisic acid (ABA) accumulations at the early stages of growth. ABA regulates the concentration of calcium (Ca\({}^{2+}\)) and RONS (e.g., OH, H\({}_{2}\)O\({}_{2}\), NO\({}_{3}^{-}\), NO\({}_{2}^{-}\)). The reactive species are easily transported through the cell membrane by diffusion and aquporins. RONS serve as nutrients and also act as signalling molecules involved in the growth process [115]. [PERSON] et al. studied the effect of PAW (produced form tap water using self-pulsing transient spark discharge) irrigation on lettuce plants.