Industrial waste sites, although extremely difficult to revegetate, may be suitable for rare plants such as Orobanche lutea that are condemned to extinction due to their low ability to compete in their natural habitats. The presence of potentially toxic metals seems to facilitate the expansion of O. lutea (parasitizing Medicago falcata) and was found in hundreds of exemplars per m2 in south Poland and potentially could spread to other localities, causing yield loss in agricultural plants. The main aim of this research was to characterize the interaction between the host, the parasitic plant and symbiotic microbes under different metal concentration in the substratum. The parasite was more common on more polluted soil and when the parasite was connected to the host, potentially toxic metals (Zn, Cd and Pb) were shared by both plants; thus, the content and concentration of these potentially toxic metals in the host were lower than those in plants without parasites. While the performance index (PIABS) of photosynthesis was lower in parasitized plants on control soil, on metal-rich industrial waste soil, PIABS was higher in the parasitized plants than in cases where M. falcata grew alone. This result suggests a role of this parasite in toxicity attenuation, although the biomass of parasitized plants and those growing on polluted sites was lower than that in control sites. In the described case, mycorrhizal colonization and arbuscular richness in M. falcata were even more highly developed on polluted sites than in control ones. The data presented support the hypothesis that the expansion of O. lutea is most likely supported by the increased concentrations of Zn and Cd in areas connected with industrial waste. Although, on industrial wastes the host yield was decreased in the parasite presence, its photosynthetic capacity was even increased.
Keywords: Arbuscular mycorrhizal fungi; Parasitic plant; Photosynthesis; Poland; Silesia-Cracow Upland; Toxic metals.
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