Plasma seed treatment has proven to be a useful technique for improving germination, growth dynamics, as well as plant resistance. In this paper, we studied the efficacy of soybean seeds treatment using various sources of cold atmospheric pressure plasma generated in air. We compared three types of plasma treatments: direct treatment with plasma generated by a diffuse coplanar surface barrier discharge (DCSBD), direct treatment with plasma generated by a multi-hollow surface dielectric barrier discharge, and indirect treatment using the gaseous products of plasma generated by an air plasma jet. The composition of plasma generated by each of the sources was analysed using optical emission spectroscopy and Fourier Transform Infrared spectroscopy (FTIR). Parameters of the plasma treatments have been optimized to improve soybean germination. Plasma-treated seeds were examined by the means of water contact angle, surface free energy and imbibition measurements, attenuated total reflectance FTIR (ATR-FTIR), x-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) analyses. Surface analysis by ATR-FTIR and XPS showed changes in the chemical bonds on the surface of the plasma-treated seeds, which led to an increase in wettability and imbibition. SEM analysis confirmed that the plasma treatment is non-invasive and does not cause changes in seed surface morphology. Among the studied sources, DCSBD proved to be the best suited for soybean seed treatment in terms of germination improvement as well as treatment time and energy efficiency.

Zea mays L. is one of the most produced crops, and there are still parts of the world where maize is the basic staple food. To improve agriculture, mankind always looks for new, better methods of growing crops, especially in the current changing climatic conditions. Cold atmospheric pressure plasma (CAPP) has already showed its potential to enhance the culturing of crops, but it still needs more research for safe implementation into agriculture. In this work, it was shown that short CAPP treatment of maize grains had a positive effect on the vitality of grains and young seedlings, which may be connected to stimulation of antioxidant and lytic enzyme activities by short CAPP treatment. However, the prolonged treatment had a negative impact on the germination, growth, and production indexes. CAPP treatment caused the increased expression of genes for heat shock proteins HSP101 and HSP70 in the first two days after sowing. Using comet assay it was observed that shorter treatment times (30–120 s) did not cause DNA damage. Surface diagnostics of plasma-treated grains showed that plasma increases the hydrophilicity of the surface but does not damage the chemical bonds on the surface.

We studied the effects of nonthermal plasma (NTP) treatment on various parameters of early germination stages of Pinus nigra seeds. In the experiment, the diffuse coplanar surface barrier discharge (DCSBD) with treatment time periods of 0, 1, 3, 5, 10, 30, and 60 s was used. Changes on the plasma-treated seed surface were studied by attenuated total reflectance-Fourier transform infrared spectroscopy. Seed germination, germination rate, germination index, length of seedling, dry seedling weight, and seedling vigor index I and II were determined in a growth test under laboratory conditions. Various statistically significant effects of seed exposure to DCSBD plasma treatment were recorded. A positive reaction was observed in the germinated seeds after exposure for 1- and 5-s. Longer exposure time periods had a rather inhibitory effect. The performance of forest nurseries of NTP modification of seeds should be evaluated in order to measure the durability of the observed growth characteristics. The potential of NTP treatment on seeds in plant ecology in future is highlighted.

Absolute densities of gaseous products generated by coplanar dielectric barrier discharge in N ₂ /O ₂ mixtures and in ambient air were determined using Fourier transform infrared (FTIR) spectroscopy. A theoretical model containing up to four molecular absorption cross sections was used to split the peaks overlapping in the FTIR spectra. The product densities were determined for a wide range of applied input powers (100–400 W). Ozone (O ₃ ) and nitrogen oxides (N ₂ O, NO, NO ₂ and N ₂ O ₅ ) were identified as the stable products of the discharge in N ₂ /O ₂ mixtures, HNO ₂ , HNO ₃ and CO ₂ were steadily present in the gas coming from the discharge in ambient air. It was found that the actual product composition strongly depends on the gas temperature. At low input power with the low gas temperature, O ₃ density was high and the NO and NO ₂ densities were very low. At a specific input power (and the gas temperature) O ₃ disappeared, while NO density started to increase gradually and NO ₂ density increased steeply. N ₂ O ₅ density increased at low input power but decreased suddenly at the same temperature when O ₃ density decreased. The influence of the gas temperature on the discharge product composition was also confirmed by the 0D chemical kinetic model and by temperature measurement. The maximal ozone density reached approximately 2.7 × 10 ²³ m ⁻³ for the input power below 150 W and the gas mixture N ₂ :O ₂ 40:60. Density of 2.6 × 10 ²² m ⁻³ was obtained for NO ₂ in the same gas mixture above 250 W.