## 1 Introduction  
The production of fruits and vegetables is an economically important segment in many regions of the world. Fresh and high-quality agriculture products with adequate content of macro and micronutrients are of a great demand as they offer good quality of life. To support the growth of the fruits and vegetables, various organic and inorganic fertilizers are used that provide plant nutrients necessary for their growth [1]. Besides the use of fertilizers, several physical methods have been used too, e.g., static magnetic fields or pulsed electric fields [2, 3]. Another promising and still novel physical method represents a cold (nonthermal, non-equilibrium) plasma. The cold plasma generated by various kinds of atmospheric pressure air discharges produces highly reactive environment of high energy electrons, radicals, and various gaseous reactive species, including \({}^{\bullet}\)OH, H\({}_{2}\)O\({}_{2}\), NOx, HNOx. When the plasma is in a contact with water, these species dissolve into water and produce so-called plasma activated water (PAW). The PAW is a mixture of long-lived reactive oxygen and nitrogen species (RONS), such as H\({}_{2}\)O\({}_{2}\), NO\({}_{2}\)\({}^{-}\) or NO\({}_{3}\)\({}^{-}\) and it is considered as a clean and sustainable alternative to chemical fertilizers. Cold plasma and plasma activated water has a potential to be effectively used in various agricultural applications [4; 5]. Most of the existing studies deal with direct plasma treatment of seed for seed disinfection, germination improvement, plant growth, etc. [6; 7; 8; 9; 10; 11; 12; 13; 14]. Besides that, indirect plasma treatment, i.e., the use of PAW or plasma activated fertilizer on seeds and plants, has recently become an interest too [15; 16; 17; 18; 19; 20; 21; 22]. The plasma generated RONS in the PAW (H\({}_{2}\)O\({}_{2}\), NO\({}_{2}\)\({}^{-}\), NO\({}_{3}\)\({}^{-}\)) may be easily transported into plant cells and act as signaling molecules in plant metabolism or can be a source of nutrients for a plant. H\({}_{2}\)O\({}_{2}\) (hydrogen peroxide) can be transported through cell membrane by free diffusion or by membrane proteins facilitating water transport (aquaporins) [23]. In the cell it can be degraded by antioxidant enzyme peroxidase or by catalase with oxygen and water as products. H\({}_{2}\)O\({}_{2}\) is the most stable reactive oxygen species (ROS) and, therefore, plays a crucial role in intracellular signaling in many physiological processes. The transport of NO\({}_{3}\)\({}^{-}\) (nitrate) into the plant cell is slower and a concentration-dependent process happening through specialized membrane transport proteins or by simple diffusion [24; 25]. NO\({}_{3}\)\({}^{-}\) is a major source of nitrogen as an essential macronutrient for plants. Moreover, NO\({}_{3}\)\({}^{-}\) may also act like signaling molecule and induce expression genes for self-transport and assimilation in the plant cell. Absorbed nitrogen could be efficiently used especially for active photosynthesis and assimilation in favor of biomass production. At last, some plants are also able to utilize NO\({}_{2}\)\({}^{-}\) (nitrite) as a nitrogen source, although, for many other plants, it can be potentially toxic [26]. To better understand the process in plants, it is necessary to focus on the effects of individual RONS components in plasma activated water (PAW). In the past, the effect of RONS was mainly investigated with respect to general visual appearance of plants and their growth parameters. However, recently, the research shifted toward analyses on microscopic and molecular level to further understand the physiological mechanisms that RONS induces in seeds and plants. For example, [PERSON] et al. treated various liquids with microwave plasma and used them to support plant vitality and sanitation effect [27]. Their results suggest that NO and NO\({}_{3}\)\({}^{-}\) contribute to the enhancement of plant growth and stress tolerance and may also play role in antimicrobial effect. [PERSON] et al.