Effects of different levels of ultraviolet (UV) on growth and some secondary metabolites of the Hairy St. Jonh’s wort (Hypericum hirsutum L.)

The production of active ingredients in medicinal plants is controlled by genetic processes, but is also strongly influenced by environmental factors. Hairy St. Jonh’s wort (Hypericum hirsutum L.)is an important medicinal plant that often grown in highlands. Since the intensity of ultraviolet in these areas is high,Therefore, in this study was investigated the effect of different levels of ultraviolet on growth and some secondary metabolites and compounds of this plant.The experiment was conducted as a pot culture with five treatments and each treatment with four repetitions.The plants were exposed to four different levels of ultraviolet including 3,5,15 and 25 Kj m-2day, and a set was considered as a control. After 51days of planting the plants that had been treated for 21days, the measurements were performed. Increasing the intensity of ultraviolet reduced the shoot fresh and dry weight, shoot length, internodes length, the content of chlorophylla and total chlorophyll and soluble sugars, each at the intensities of 25 kJm-2day.The concentrations of phenols, flavonoids and malondialdehyde significantly increased with increasing of ultraviolet radiation intensity and highest concentrations were detected at25 kJ m-2day.The concentrations of anthocyanins and hydrogen peroxide in plants treated by 5and15 kJ m-2day; and the concentrations of carotenoids in plants treated by 3and 5kJ m-2day showed a significant difference with the control.The results of this study showed that the collection of seeds of Hypericum hirsutum from a height of about 2110 meters due to the presence of ultraviolet rays caused a change in the biochemical composition of the plant .