**Ethics**

positively affected by the cold radiofrequency air plasma treatment. The MDS conditions used in our work represent the naturally occurring conditions typical for seedbeds, where no free water is usually present, but water is given abundantly and then drained. HDS conditions represent lower water availability, causing water stress during germination. It should be emphasized that seed germination and early seedling growth are critical stages for plant establishment, and plants are more sensitive to drought stress during these stages [33]. Our results support the findings reported recently by investigators, which studied the influence of the cold plasma treatment on the oilseed rape (*Brassica napus* L.) seed germination under drought stress [31]. Ling et al. reported that, under drought stress, cold plasma treatment significantly improved the germination rate by 4.4–6.25% for various species of the oilseed rape [34]. Seedling growth characteristics, including shoot and root dry weights, shoot and root lengths, and lateral root number, were significantly improved after the cold plasma treatment. It is noteworthy that in our experiments the similar improvement of the germination rate was obtained and confined in the range of 1–12% for pepper and tomato seeds at 21°C, under various conditions of restricted water availability. Indeed, for tomato seeds it was shown that there is a direct relationship between uptake of water and germination rate (this conclusion is supported by recent results reported by other groups [35]), while for pepper seeds, no such correlation was found. This means that other possible effects of PT are responsible for the improvements in germination rates of pepper under plasma treatment (such as

In addition, it was also shown that temperature plays a key role in the effect of plasma on seed germination of pepper. Our experiment demonstrates that at a high temperature of 27°C, in WW conditions, germination rates of non-PT pepper seeds were much higher than the rates of treated seeds, grown under MDS and HDS. The rates of germination of PT seeds were higher than those of WW-grown pepper seeds but considerably lower than those at 21°C. The reason for the drastic decrease in germination rates of PT seeds under WW conditions at higher temperatures remains unclear and would be further investigated. For tomato seeds the differences between germination rates at 27°C and those at 21°C were not so dramatic. These preliminary results demonstrate the importance of determining the right combination of germination temperature and PT duration for each cultivar tested. They may explain some of contradictory effects in investigations of the impact of plasma treatment on germination rates and germination speeds found reported by other

The influence of the cold radiofrequency air plasma treatment on the imbibition and germination of tomato and pepper seeds exerted to conditions appearing in natural seedbeds has been investigated. Plasma treatment markedly hydrophilized surface of seeds and increased the water imbibition (absorption). Various conditions of water supply to germinated seeds were studied. Drought stress essentially affected both germination rates and the kinetics of seed germination.

the regulation of energy metabolism [36]).

researchers.

134 Advances in Seed Biology

**5. Conclusions**

Does not apply.
