Tumbleweed

Abstract: Experiments were conducted to determine the differential absorption of Cr species by tumbleweed (Salsola kali) as well as the effect of this heavy metal on plant growth and nutrient uptake. Tumbleweed seeds were grown in an agar-based media containing different concentrations of either Cr(III) or Cr(VI). The results demonstrated that the uptake of Cr was influenced by the Cr concentration in the growth medium and the speciation of this heavy metal. When supplied in the hexavalent form, the concentration of Cr in the different plant parts (2900, 790, and 600 mg kg−1 for roots, stems, and leaves, respectively) was between 10 and 20 times higher than the amounts found when Cr was supplied in the trivalent form. In addition, it was found that in most of the experiments, Cr(III) exhibited more toxic effects on tumbleweed plants than Cr(VI). The size of roots of plants grown in 20 mg L−1 Cr(III) were significantly smaller (p < 0.05) than those grown in 20 mg L−1 Cr(VI). Plants exposed to 20 mg L−1 Cr(III) produced shoots significantly shorter (p < 0.05) compared with the size of control plants and with those grown in 20 mg L−1 Cr(VI). In addition, the absorption of macronutrients and microelements was in general lower when the plants were grown in the medium containing Cr(III). The amounts of Cr concentrated in the aerial plant parts under experimental conditions may indicate tumbleweed as a new option for the phytoremediation of Cr-contaminated soil.

Abstract: Although arid and semiarid regions account for about 40% of world land, no nanotoxicity studies on desert plants have been reported. In this investigation, Parkinsonia florida (blue palo verde), Prosopis juliflora-velutina (velvet mesquite) and Salsola tragus (tumbleweed) were selected to determine the phytotoxicity of ZnO nanoparticles (NPs) at germination stage. Seeds were treated with ZnO NP concentrations ranging between 0 and 4000 mg L−1. From this, the germination rate, root elongation and Zn concentration in tissues were determined. Furthermore, X-ray Absorption Spectroscopic (XAS) studies were performed to obtain preliminary information on potential NP biotransformation within plant tissues. Results indicated that germination was not significantly affected (P < 0.05) in any of the three plant species. Also, root elongation in blue palo verde was reduced by 16%, with respect to control at 4000 mg ZnO L−1. Tumbleweed root size diminished by 14% and 16% at ZnO NP levels of 500 and 2000 mg L−1, respectively, and velvet mesquite root length was reduced to all ZnO NP concentrations used in this study. The 50% inhibitory concentration (IC50) for mesquite root elongation was between 1000 mg L−1 and 2000 mg L−1. XAS results demonstrated that ZnO NPs were biotransformed on/within the root and Zn was present as Zn(II) in the three desert plant species.