Distribution of chromium and its effect on morphology and anatomy of Brassica juncea (Indian mustard) and soil microorganisms

Brassica juncea (Indian mustard) was grown under greenhouse conditions in field-moist or air-dried soils, amended with 100 mg kg-1 Cr (III or VI). The plant concentrated Cr mostly in the roots and was tolerant of both metal treatments. Cr (VI) appeared to be more toxic to both soil microorganisms and plant than Cr (III). Root growth and anatomical characteristics were inhibited to a greater extent than those of shoots. Soil chemical analyses and X-ray absorption near-edge spectroscopy (XANES) detected Cr (III) species in Cr (VI) treatment. The XANES and X-ray microprobe spectroscopy data revealed nearly complete conversion of Cr (VI) to Cr (III) in the roots, where it was accumulated as Cr (III)-acetate (72%) preferentially in epidermis and cortex, while, in the leaves, as Cr (III)-oxalate (81%) in epidermis and spongy mesophyll. The ability of B. juncea to tolerate and detoxify Cr (VI) makes this plant a potential candidate for phytostabilization.