Distribution of selenium and phenolics in buckwheat plants grown from seeds soaked in Se solution and under different levels of UV-B radiation

Seeds of common buckwheat (Fagopyrum esculentum) were soaked in water, sodium selenate (5, 10 or 20 mg SeVI/L), or sodium selenite (10 or 20 mg SeIV/L) solutions. Plants grown from soaked seeds were exposed to reduced UV-B radiation, ambient, or enhanced UV-B. The mass fraction of selenium in leaves was much higher in plants obtained from seeds soaked with selenate (up to 185 ng/g) in comparison to selenite (up to 103 ng/g). In plants obtained from seeds soaked in water, regardless of UV-B levels, the highest concentration of selenium was found in leaves, where the values were between 45 and 66 ng Se/g. In buckwheat leaves 44.5–63.6 mg/100 g d.m. of fagopyrin was found, and in stems 14.3–26.4 mg/100 g d.m.; here no influence of seed soaking solution or UV-B exposure was found. The content of total flavonoids in leaves was 7.8–15.9% and in stems 1.4–4.1%.