The effect of high-frequency 5.28 MHz plasma and radio wave seed treatments on red clover growth, nodule formation and isoflavonoid content has been investigated. The short-term and long-term effects of plasma and radio wave treatment of seeds were evaluated on clover plants during two years of vegetation. The response of plants to plasma treatment was increment in root growth and the nodule formation. Significant changes in the length and weight of roots were noted in the first year of vegetation. The increase in isoflavonoids content observed after plasma and radio wave treatments can be explained by the advancement in nodulation process.

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Chitosan‐caffeic and chitosan‐ferulic acid conjugates are synthesized by carbodiimide method and characterized by UV, FTIR, and NMR spectroscopy. There are two obtained forms of conjugates: freshly synthesized and reconstituted freeze‐dried. A comparative study of the stability of various conjugate forms over time and under UV irradiation has been carried out. It has been shown that the absorption intensity of an aqueous solution of the freshly synthesized chitosan‐caffeic acid conjugate decrease in ~2 times during 20 weeks of storage, while the maximum rate of intensity decrease is observed during the first 40 days. The absorption intensity of the chitosan‐ferulic acid conjugate decrease by 6–7% during the entire storage period. It has been found that freeze‐dried powders of chitosan‐caffeic and chitosan‐ferulic acid conjugates are stable for at least 1 year. It has been established that freeze‐dried chitosan‐caffeic and chitosan‐ferulic acid conjugates are more stable under UV irradiation (in 4–8 and 1.4–1.9 times, respectively) compared to freshly synthesized ones. A comparative study of the influence of conjugates on barley seedlings (Hordeum vulgare L.) growth has been carried out.

The effect of seed treatment with various materials of chitosan and hydroxycinnamic acids on the growth of barley seedlings was evaluated. It was shown that chitosan-hydroxycinnamic acid conjugates and nanoparticles had no negative effect on the initial stages of the growth of barley seedlings. Adaptation of seedlings after 24 h exposure to 4 % NaCl in the samples of conjugates of 30 kDa chitosan with caffeic and ferulic acids was more effective. There was a decrease in proline contents and restoration of the growth activity under post-stress conditions.

It was established that the treatment of clover seeds with radio frequency (RF) electromagnetic field and low pressure (200 Pa) RF plasma excited at a frequency of 5.28 MHz has a stimulating effect both on the germination of seeds and on the growth and development of plants grown in laboratory and field conditions. Plasma treatment for 5 min led to the greatest stimulation of seed germination and germination energy, a significant increase in the biomass of shoots and roots. At the same time, the content of phenolic compounds and flavonoids in plant leaves decreased.