Effects of Glomus deserticola inoculation on Prosopis: Enhancing chromium and lead uptake and translocation as confirmed by X-ray mapping, ICP-OES and TEM techniques

Arbuscular mycorrhizal (AM) fungi contribute to plant growth, mediating the uptake of mineral elements. In polluted areas, AM also binds toxic heavy metals to roots. In this study, mesquite plants (Prosopis sp.), associated with Glomus deserticola, were treated for 15 days (in hydroponics) with lead at 0, 10, 50, or 100 mg L−1, and chromium(III) and (VI) at 0, 20, 40, 75, or 125 mg Cr L−1. All Cr ion concentrations and the highest Pb concentration reduced shoot size compared to the control. Toxic effects (yellowish leaves, leaf decay) were observed after seven treatment days. However, Pb and Cr(III) treated plants recovered upon conclusion of experimental period. Total amylase activity in leaves increased upon the addition of Pb and Cr. The inductively coupled plasma-optical emission spectroscopy results showed that plants treated with Pb at 50 mg L−1 accumulated in roots, stems, and leaves: 61947, 9584, and 478 mg Pb kg−1; whereas plants treated with Cr(III) and Cr(VI) at 125 mg L−1 accumulated 28815, 6055, and 647; and 13767, 5010, and 2530 mg Cr kg−1. The transmission electron microscopy (TEM) micrographs showed the presence of G. deserticola within roots. X-ray mapping demonstrated higher Cr and Pb deposition in xylem and phloem cells. Results suggest that G. deserticola improves metal tolerance/accumulation in mesquite.