Effect of Plasma Activated Water, Hydrogen Peroxide, and Nitrates on Lettuce Growth and Its Physiological Parameters

• Main Authors: Katarína Kučerová, Mária Henselová, Ľudmila Slováková, Michaela Bačovčinová, Karol Hensel
• Format: Article
• Language: English
• Published: MDPI AG 2021-02-01
• Series: Applied Sciences
• Subjects: plasma activated water; plasma agriculture; hydrogen peroxide; nitrates; lettuce; growth enhancement
• Online Access: https://www.mdpi.com/2076-3417/11/5/1985
• ISSN: 2076-3417

Cold plasma generated by atmospheric pressure air discharge is a source of various gaseous reactive oxygen and nitrogen species (RONS). When the plasma is generated in a contact with water, the RONS dissolve into water, change its chemical composition, while producing so-called plasma activated water (PAW). The PAW has the potential to be effectively used in various agricultural applications, as the long lived liquid RONS (H₂O₂, NO₂⁻, NO₃⁻) may act like signaling molecules in plant metabolism or serve as nutrients. We studied the effect of the PAW on lettuce plants and compared it with the effect of H₂O₂ and/or NO₃⁻ solutions of various concentrations to assess their role in the PAW. The PAW was generated from tap water by DC driven self-pulsing transient spark discharge. Pre-grown lettuce plants were cultivated in pots with soil and irrigated with the PAW or solutions of H₂O₂ and/or NO₃⁻. After 5 weeks the growth parameters, number and quality of leaves, fresh and dry weight of plants, photosynthetic pigment (chlorophyll a + b) content, photosynthetic rate, and activity of antioxidant enzymes (superoxide dismutase, SOD) were evaluated. Lettuce plants irrigated with the PAW in comparison with chemically equivalent solution of H₂O₂ and NO₃⁻ had similar dry weight; however, the PAW induced higher photosynthetic pigment content, higher photosynthetic rate, and lower activity of SOD. The NO₃⁻ mainly contributed to the increase of dry weight, photosynthetic pigment content, photosynthetic rate, and overall better appearance of plants. The H₂O₂contributed to an increase of dry weight and induced SOD activity. In general, H₂O₂ and NO₃⁻ in proper concentrations can stimulate plant growth and affect their physiological properties.