in all the studied cases, carnivory allows plants to grow and reproduce using animals as a source of nitrogen, phosphorus and possibly potassium. however, there is a spectrum of dependency on animal prey. pygmy sundews are unable to use nitrate from soil because they lack the necessary enzymes (nitrate reductase in particular). common butterworts ("pinguicula vulgaris") can use inorganic sources of nitrogen better than organic sources, but a mixture of both is preferred. european bladderworts seem to use both sources equally well. animal prey makes up for differing deficiencies in soil nutrients.