Medicinally Important Secondary Metabolites and Growth of Hypericum perforatum L. Plants as Affected by Light Quality and Intensity

Abstract

Hypericum perforatum L. (St. John's wort) is a traditional medicinal plant that is mainly used for the treatment of neurological disorders and depression. The present study was undertaken to investigate the effects of different light quality, including blue, white, and red light, in combination with two light intensities, 250 and 500 μmol m^-2s^-1 photosynthetic photon flux (PPF) on the concentrations of medicinally important secondary metabolites in the leaf tissues and growth of H. perforatum plants. The results revealed that growth was greatest in those plants grown under white and red light with 500 μmol m^-2s^-1 PPF. The hypericin and pseudohypericin contents of the plants grown under red light with 250 μmol m^-2s^-1 PPF were 1.9 and 1.9 times higher, respectively, than those grown under red light with 500 μmol m^-2s^-1 PPF. The differences in contents between blue and white light treatment were not significant for plants grown with 250 μmol m^-2s^-1 PPF. Our result revealed that the contents of medicinally important secondary metabolites in the tissues of H. perforatum plants can be altered by controlling the light environment.