Effect of light intensity on growth traits, photosynthetic and total hypericin in Topaz cultivar and Mishu ecotype of Hypericum perforatum

Hypericum perforatum L. (St. John's wort) is a perennial herb which contains precious metabolites such as hypericin, pseudo-hypericin and hyporforin widely used in the treatment of mild to moderate depression.  In order to evaluate light density (three levels including full light condition, 75% and 50% of full light intensities) on plant height, gland number per leaf, stomata number, chlorophyll content, fresh and dry weight, as well as hypericin production of Topaz cultivar and Mishu ecotype of H. perforatum under hydroponic conditions in the greenhouse, an experiment was carried out as split plots based on randomized complete blocks design with three replications at the University of Tabriz in 2017. The chlorophyll and hypericin contents were used by spectrophotometry. The results showed that the light density significantly affected on fresh and dry weight, plant height, gland number per leaf, chlorophylls a and b, photosynthesis and total hypericin content in the H. perforatum. The highest fresh and dry weight, gland number per leaf, stomata number, photosynthesis and total hypericin content were belonged to the full light conditions (100% light). The highest plant height, chlorophyll a and b were belonged to the 50% of prevalent light intensity. The results indicated that Topaz cultivar is better than Mishu ecotype. In conclusion, increasing hypericin content in Hypericum perforatum by managing of light intensity is possible