## 3 Effects of Plasma on Plant Vegetative Growth and Reproduction
Elevated in situ H\({}_{2}\)O\({}_{2}\) and NO\({}_{x}\) concentrations in tomato seedlings in response to plasma-activated water (PAW) was detected by [PERSON] et al. [61]. Similar observations the accumulation of RONS in response to plasma treatment in plants have also been reported in other studies [43; 54]. The impact of RONS on plant development is well known [76; 77], so plasma-generated RONS may similarly influence plant growth and development. Redox reactions play an important role in the cell cycle and cytokinesis. Many small antioxidants (i.e., ascorbate and glutathione) are essential for the cell cycle and act as redox buffers [78; 79]. A study of wheat (_Tritcium sp._) and Arabidopsis roots suggests that the chemical impediment of ROS disturbs microtubule assembly and promotes microtubule formation in the root tip cells. This disturbance to tubulin organization leads to a distorted cytokinesis process [80]. ROS, such as H\({}_{2}\)O\({}_{2}\), hydroxyl radical (OH\({}^{\bullet}\)), and superoxide (O\({}_{2}\)\({}^{-}\)\({}_{\bullet}\), affect cell expansion via their control of the cell wall rigidity. Peroxidase in the apoplasts maintains the H\({}_{2}\)O\({}_{2}\) level, regulates the crosslinking of phenolics and extensins, and maintains the cell wall rigidity. In contrast, OH\({}^{\bullet}\) oxidizes polysaccharides (e.g., xyloglucans and pectins) and facilitates cell wall loosening [76]. Another study showed that the O\({}_{2}\)\({}^{-}\)\({}_{\bullet}\) gradient in the meristem of the roots can play a role in cell division--high O\({}_{2}\)\({}^{-}\)\({}_{\bullet}\) levels are present in root tips, the highest cell division zone, and the peripheral elongation zone has high H\({}_{2}\)O\({}_{2}\) levels [81]. In _Arabidopsis_, the ROS content varies during floral bud formation and maturation, indicating the crucial role of ROS during flower development. In rice, the MADS3 gene, which is responsible for stamen formation during early floral bud development, regulates the O\({}_{2}\)\({}^{-}\)\({}_{\bullet}\) concentration. Abnormal MADS3 expression causes pollen sterility by accumulating O\({}_{2}\)\({}^{-}\)\({}_{\bullet}\)[82]. ROS can crosstalk with phytohormones and influence plant growth and development. In the roots, meristem cell growth is influenced by the interplay of H\({}_{2}\)O\({}_{2}\) and brassinosteroids (BRs); intracellular H\({}_{2}\)O\({}_{2}\) induces the binding of BR to its receptor kinase BRI. H\({}_{2}\)O\({}_{2}\) can oxidize BZR1 (Brassinzole-Resistant 1) and BES1 (Brassinosteroid insensitive 1-Emssuppressor 1), the key transcription factors of BR signaling, and modify their activities. BZR1 interacts with PIF4 (Phytochrome Interacting Factor 4) and ARF6 (Auxin Response Factor 6), which are responsible for promoting meristem growth and development [83]. The redox reaction and ROS also regulate the post-translational modification of histones, transcription factors, and the chemical modifications of the nitrogenous DNA bases. Therefore, ROS epigenetically regulates plant growth. Under oxidative stress, ROS downregulates the histone demethylase gene, interacts with DME1 (DNA methylase), and epigenetically modifies the stress response of plants [77]. Seed reserve food utilization and the contents of soluble sugar and protein in seedlings are elevated after plasma treatments [84]. Cold atmospheric pressure plasma treatment of seeds affects the growth hormone concentration in the vegetative stage. [PERSON] et al. [27] observed that the concentration of auxin (IAA) was upregulated in 14- and 21-day-old seedlings exposed to LTP (low-thermal plasma) for 120 s and 600 s at the seed stage. Interestingly, the cytokinin content was also significantly increased in 14 days old seedlings exposed to LTP for 120 s (compared to non-exposed seedlings) [27]. Other reports suggest that the redox homeostasis of plants is modified by cold atmospheric or low pressure plasma treatment.