Element accumulation by the holoparasitic species Cuscuta planiflora from serpentines in Bulgaria

The holoparasitic species Cuscuta planiflora Ten. (Convolvulaceae) parasitizes the Ni hyperaccumulator Odontarrhena muralis (Waldst. & Kit.) Endl. and a non-hyperaccumulator, Sanguisorba minor Scop., in Bulgarian serpentine areas. This study investigated the host/parasite relationship to evaluate: (1) metal accumulation in different parts of the parasite and the host and (2) its potential threat to Ni phytomining/agromining by suppressing growth of the hyperaccumulator. Elemental concentrations in soil, shoots, leaves, and inflorescences of the two host plants, and in shoots and inflorescences of the parasite, were determined. Elemental concentrations of Ca, Mg, Fe, Ni, Cr, Co, Zn, Cu, Mn, Cd, and Pb were determined after microwave digestion using inductively coupled plasma—optical emission spectrometry (ICP-OES) under optimal instrumental parameters. Individuals of hosts, both infected and non-infected, differed in the concentrations of essential elements (P, K) and some micronutrients. Infected individuals of O. muralis showed lower Ni concentrations in shoots, leaves, and inflorescences compared to non-infected ones. Sanguisorba minor is an excluder plant with low tissue Ni concentrations. The parasite had higher P and K, and lower Ca, Mg, Ni, Zn, Co, and Mn concentrations, than the host. The highest Ni concentration measured in the shoots of C. planiflora was 279 mg kg⁻¹, whereas that from S. minor was 29.9 mg kg⁻¹. Element transfer from host to parasite appeared element-specific and after infection Ni concentrations in all organs and biomass of hosts were reduced. We conclude that infection by C. planiflora is a potential threat to use of O. muralis for Ni agromining.