6. Dr. Ofir Katz

Parasitic plants sequester various resources from their hosts, but the selectivity of this resource sequestration and its impacts on host plant’s chemistry are not fully understood. I studied the elemental composition of theholoparasitic plant Cistanche tubulosa and its host, the salt-accumulating Atriplex halimus in the southern Judean Desert as a case study. Essential elements, phosphorus and potassium, are taken up actively by C. tubulosa, probably owing to their particular importance for the parasite (including maintaining a strong transpiration gradient). Results for the essential calcium are less conclusive. Elements that are beneficial but not essential, silicon and zinc, are taken up passively. C. tubulosa excludes chlorine, which binds with sodium in the host A. halimus. It might be that A. halimus plays a role in reducing salinity (sodium) stress for C. tubulosa that infect it, a supposition supported by C. tubulosa preferring salt-accumulating hosts. Sulphur and strontium contents in host A. halimus plants are probably higher than in non-host plants, suggesting a defensive role for these elements. In reference to strontium, this is a first indication for its possible role in plants and a potential mechanism to improve phytoremediation of strontium-polluted soils.