Regional differences in hypericin and pseudohypericin concentrations and five morphological traits among <i>Hypericum perforatum</i> plants in the northwestern United States

Abstract

Geographic differences among Hypericum perforatum L. plants in concentration of two hypericins and five morphological characteristics were analyzed in plants collected from four sites each in northern California and western Montana and two sites in Oregon. Differences among regional collections of H. perforatum were assessed based on analysis of hypericin and pseudohypericin concentration in floral, leaf, and stem tissue; light and dark leaf gland density; leaf area; leaf length/width ratio; and stem height. Significant differences in morphological and biochemical traits were detected primarily between samples collected from California and Montana. California samples had higher concentrations of hypericins, greater leaf gland density, larger leaves, and taller stems than those from Montana. Overall, Oregon samples did not consistently differentiate from those of Montana and California. Seasonal differences in hypericins were analyzed in Oregon plants only. Mean floral concentration of pseudohypericin (0.29%) and hypericin (0.06%) were highest during anthesis coinciding with July and August sampling dates, whereas mean leaf concentrations (0.19 and 0.04%, respectively) were highest in August.Key words: Hypericum perforatum, hypericin, St. John's wort, leaf glands, noxious weed, medicinal plant.