The Effects of Red Clover Seed Treatment with Cold Plasma and Electromagnetic Field on Germination and Seedling Growth Are Dependent on Seed Color

Featured Application The results of this study have the potential for application in agriculture for increasing the production of red clover biomass. This study aimed to estimate the effects of cold plasma (CP) and electromagnetic field (EMF) treatment of red clover (Trifolium pratense) seeds with different coat colors on germination kinetics, the content of seed phytohormones, and the growth of seedlings. Seeds of red clover cultivar 'Arimaiciai' were treated with radio-frequency EMF or capacitively coupled low-pressure CP for different durations. There were no differences in germination kinetics between yellow, brown, and dark purple seeds in control, but the germination rate of seeds treated with CP and EMF depended on seed color: The germination of yellow seeds was stimulated stronger compared to dark purple and brown seeds, and EMF did not stimulate germination in brown seeds. The content of phytohormones in control seeds and the shift in their amount induced by seed treatments were also strongly dependent on seed color. No relationship was found between the effect on germination kinetics and changes in phytohormone levels. In the control, seedlings growing from the yellow seeds were heavier, and the number of root nodules was 12.5 times larger compared to seedlings of dark purple seeds. Seed treatments with CP and EMF significantly increased the number of root nodules, and this effect was stronger in seedlings from dark purple seeds compared to those from yellow seeds.