**1. Introduction**

Interaction of cold plasmas with plant seeds has drawn the evident attention of scientists in the last decade [1–8]. The investigators mainly concentrated on the possibility to control the germination by exposure of seeds to various types of plasma, including atmospheric and lowpressure plasma discharges. It should be stressed that experimental data related to the influence of plasma treatment (carried out with capacitive and inductive discharges) on the germination time and percentage are contradictory. The first profound investigation of the impact of plasma discharges on seed germination was reported by Volin et al. [1]. These authors exposed seeds

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

of radishes (*Raphanus sativus*) and two pea cultivars (*Pisum sativum* cv. "Little Marvel" and *P. sativum* cv. "Alaska") to CF<sup>4</sup> and octadecafluorodecalin plasma and observed an essential delay in germination [1]. Since then, investigators focused on the following main fields: (1) decontamination of seeds by plasma, (2) breaking of dormancy with plasma, (3) the impact of plasma treatment (PT) on the rate and kinetics of germination, and (4) impact of PT on the root generation (sprouting).

Decontamination and inactivation of pathogenic microorganisms of seeds by PT have been communicated recently by various groups [2, 3, 5, 6]. Nishioka et al. reported the effectiveness of low-pressure plasma treatment in the inactivation of the seed-borne plant pathogenic bacteria [6]. Researchers reported the impact of PT on germination, sprouting, and dormancy breaking of seeds. Sera et al. investigated the influence of PT on wheat and oat germination. The authors reported that PT did not affect germination of oat seeds, but they did note accelerated root generation in plants grown from plasma-treated seeds [7]. The same group also communicated that PT did change seed germination in Lamb's Quarters seeds [8]. Similar results were reported for wheat seeds (*Triticum aestivum*) by Dobrin et al. [9].

In contrast, Ji et al. communicated the significant improvement of the germination rate of *Coriander sativum* under nonthermal atmospheric pressure treatment [10]. Dhayal et al. showed about 50% increase in the germination rate, and the activity was increased twice after plasma treatment of safflower [11]. The essential augmentation of the germination rate by low-temperature plasma treatment was registered by Stolárik et al. for pea (*Pisum sativum* L. var. Prophet). Stolárik et al. related the observed effect to the chemical modification of the pea surface by plasma [12]. These results support the observations of the modification of the physical structure of seed coat by the low-pressure argon gas discharge reported by Dhayal et al. [11].

A stimulating effect of cold plasma on both the germination and sprouting of tomato seeds (*Lycopersicon esculentum L. Mill*. cv. "Zhongshu No. 6") has been reported [13]. Similar results were reported for *Pauwlonia tomentosa* seeds [14]. Kitazaki et al. studied growth enhancement of radish sprouts (*Raphanus sativus* L.) induced by low-pressure O2 radiofrequency plasma irradiation [15]. Dobrin et al. reported that the roots and sprouts of plasma-treated wheat seeds (*T. aestivum*) were longer and heavier than those of the nontreated seeds [9]. The improvement of the germination rate of the seeds of legumes and grain crops (*Lupinus angustifolius* (blue lupine), *Galega virginiana* (catgut), and *Melilotus albus* (honey clover and soy)) by low-pressure (5.28 MHz) plasma was reported by Filatova et al. [16].

The experimental results revealed that oxygen-related radicals strongly enhance growth, whereas ions and photons do not [15]. The positive effect of cold helium plasma treatment on seed germination, growth, and yield was reported recently for wheat [17]. Treatment of spinach seeds by magnetized arc plasma increased the germination rate by 137% [18]. It has been demonstrated that cold atmospheric plasma treatment had little effect on the final germination percentage of radish seeds, but it influenced their early growth [19]. The contradictory data related to the impact of plasmas on the seed germination were summarized in the recent review by Randeniya and de Groot [20]. Ji et al. suggested that plasma can enhance seed germination by triggering biochemical processes in seeds [4].

Basically, the investigators admit that cold plasma treatment is an efficient and "green," non-waste method to improve seed germination and crop yield. It plays essential roles in a broad spectrum of biological processes in plants, including reducing the bacterial bearing rate of seeds, modification of the seed coat chemical composition, hydrophilization of seed coats, homogenization of the kinetics of germination, and influence on the seedling growth [16, 21].

Our group recently reported the impact of cold air plasma on the surface properties of lentils (*Lens culinaris*) and beans (*Phaseolus vulgaris)* [22, 23]. We established that cold plasma treatment leads to essential hydrophilization of the cotyledon and tissues constituting the testa when they were separately exposed to the plasma discharge. Contrastingly, when the entire bean is exposed to plasma treatment, only the external surface of the bean has been hydrophilized by the cold plasma [23]. The pronounced hydrophilization of seeds by plasmas was reported also by other groups [9, 21]. Actually, the effect of hydrophilization of natural organic surfaces by plasma treatment has been already extensively studied [24, 25].

The cold plasma treatment, which inspired change in wettability, is followed by a consequent change in the water imbibition of the seeds [9, 22, 23]. At the same time, the relation between the change in the wettability, induced by the plasma treatment of seeds, and the parameters of germination (time and rate) remains obscure. In our paper we address the problem of the impact of the cold radiofrequency air plasma treatment, performed with the inductive plasma discharge [24], on the germination of seeds exerted to various conditions of water availability. The main goal of the research is the establishment of the influence of cold plasma treatment on the germination rate and kinetics under the conditions of limited water supply conditions.
