Metal hyperaccumulator plants may be defended from herbivore/pathogen attack by elevated tissue metal contents. We encountered the parasitic plant Cuscuta californica growing on a Ni hyperaccumulator (S. polygaloides) and investigated this host/parasite relationship. Elemental levels in plant samples, and the Ni level in soil samples, were measured for two hosts: S. polygaloides and the non-hyperaccumulator Lessingia nemaclada. Levels of 12 elements in parasitized and nonparasitized hosts, and corresponding C. californica samples, varied only for S. polygaloides, where significant variation was detected for six elements. Parasitized and nonparasitized S. polygaloides had similar amounts of Ni, K, P, Co, and Pb, but parasitized plants had higher Ca than nonparasitized ones. Cuscuta had higher K and P, and lower Ni, Co, and Pb, than host S. polygaloides. Dodder parasitizing S. polygaloides contained 800 mg/kg Ni, whereas that from L. nemaclada contained only 11 mg/kg Ni. We concluded that hyperaccumulated Ni did not defend S. polygaloides against attack by Cuscuta. Furthermore, the Ni content of Cuscuta parasitizing S. polygaloides probably is sufficient to have a defensive effect against herbivores attacking Cuscuta. Thus, we suggest that this is a case of a parasite obtaining an elemental defense from its host plant.

Key words: Cuscuta, metal hyperaccumulation, nickel hyperaccumulation, parasitic plant, plant defense, Streptanthus