Seed treatment with cold plasma and electromagnetic field improves germination, plant growth and increases the amount of phytoestrogens in the leaves of Red Clover (Trifolium pratense)

Abstract

Red clover (Trifolium pratense L) is widely used as a fodder plant as well as a dietary supplement marketed for use in alleviation of menopausal symptoms or treatment of prostatic diseases. Commercial extracts of red clover contain estrogenic isoflavones, with formononetin (F) and biochanin A (BA) found in the largest amounts. We studied the effects of pre-sowing seed treatment, using radio-frequency electromagnetic field (EMF, 10 and 15 min) and cold plasma (CP, 5 and 7 min), on germination, growth and biochemical traits of seedlings of two cultivars of red clover – ‘Vyčiai’ and ‘Sadūnai’. The impact of treatments on morphological traits, nutritive value (crude protein content, digestibility, etc. measured by near-infrared spectroscopy) and concentration of isoflavones F and BA (by HPLC analysis) was estimated in leaves of plants grown in the experimental plots for 5 months. The germination tests in vitro revealed that CP treatments increased germination rate, and this effect was more pronounced for ‘Vyčiai’ (germination rate increased up to 24%). EMF treatments did not affect germination indices, only EMF (15 min) reduced germination percentage of ‘Sadūnai’ by 12%. Treatments induced changes in plant morphometric parameters were dependent on cultivar of red clover. The average number of stems per one plant for ‘Vyčiai’ was increased from 26 to 40% in all treated groups, in comparison to control, whereas the number of stems of ‘Sadūnai’ cultivar was not affected by seed treatments. Dry weight of ‘Vyčiai’ plants in CP (5 min) and EMF (15 min) groups was by 37 and 43% larger, dry weight of stems was by 36 and 42%, dry weight of leaves – by 49 and 34% larger in comparison to control, respectively. Treatment induced positive morphometric changes for ‘Sadūnai’ were less pronounced and EMF (10 min) induced decrease in dry weight (-20%) of plants and weight of leaves (-14%).[...]