Furanocoumarins in Wild Parsnip: Effects of Photosynthetically Active Radiation, Ultraviolet Light, and Nutrients

Abstract

Previous studies of wild parsnip, Pastinaca sativa L., revealed a significant degree of genetically controlled variation in furanocoumarin production. In this study, the influence of environmental factors, namely, soil nutrients, photosynthetically active radiation, and ultraviolet (UV) radiation, on the production of furanocoumarins in the wild parsnip was examined experimentally. Aboveground tissues of plants grown under all combinations of three light intensities and three nutrient levels (N, P, K) were analyzed for the absolute and relative amounts of furanocoumarins. In a second experiment the effect of ultraviolet radiation on furanocoumarin production was evaluated by growing plants under full sunlight with and without an ultraviolet screen. Light and nutrient availability jointly affected the concentration of four of the six furanocoumarins present (sphondin and angelicin being the exceptions). Both nutrients and light were limiting factors in furanocoumarin production insofar as low availability of either resource limited the effect of variation in other resource. Relative amounts of the furanocoumarins were independently influenced by light and nutrient availability. UV radiation increased the concentration of all but two of the furanocoumarins (imperatorin and sphondin) and also influenced that relative amounts of furanocoumarins. Since furanocoumarins are UV—phototoxic to many organisms, including insects, the response of parsnip plants to UV radiation may affect their resistance to herbivores.