Chromium accumulation, transport and toxicity in plants∗

Abstract

The predominant pathway for human exposure to chromium in non-occupationally exposed individuals is via food with a daily intake of around 30-100 µgd -1 , with vegetables providing a major contribution. Unlike reports of chromium essentiality to man and animals, plants appear not to require chromium in spite of some early reports of a stimulatory growth effect.Most reports on chromium in plants have been concerned with their growth on soils amended with sewage sludge, pF-ash, tannery waste, or on ultra basic soils, which contain extreme concentrations of the element. Experimental studies with plants grown in hydroponic solution have often been undertaken at unrealistically high concentrations to examine the uptake of chromium in various forms, either as CrIII or CrVI at different pHs. In most cases, reports on chromium in plants deal with element concentrations and plant/soil relationships rather than detailed biochemical and physiological processes.In general, chromium is largely retained in the roots of plants, although the oxidation state of chromium, pH, presence of humates and fulvates and plant species, affect plant uptake and transport. Leaves usually contain higher concentrations than grains. The uptake of CrIII is largely a passive process, whereas CrVI uptake is a metabolically mediated process via the sulphate pathway and is thus readily transported around the plant. The presence of a compound similar to trioxalate CrIII has been recorded while little chromium has been reported to be associated with cell organelles or soluble proteins.

Comparative Use of Soil Organic and Inorganic Amendments in Heavy Metals Stabilization

“…Chromium was initially adsorbed by soil carbonates as compared with soil organic matter (P < 0.001) [42,43]. In contrast, at the end of the experiment, a Cr redistribution among fractions was observed and the Cr fraction organic associated to the soil organic matter increased by 10% in the BC treatment, as compared to the beginning of the experiment.…”

Copper-induced toxicity in aquatic macrophyte, Hydrilla verticillata: effect of pH

“…Evidence suggests that the uptake of ions by submerged leaves may be linked to the photosynthetic utilization of bicarbonates. The maximum uptake of metals takes place within a few hours at sublethal concentrations (Smith et al 1989) with few exceptions where uptake is gradual. However, Sutton and Blackburn (1971) reported a maximum uptake of Cu in H. verticillata at 2 p.p.m, after 4 days, while higher concentrations were toxic and resulted in a decline of uptake.…”

Does the EU migration level of chromium VI in toys need to be lowered?

“…However, in some environments (e.g. serpentine rocks), mean concentrations of chromium in naturally occurring soils are higher: 2,221 mg chromium VI/kg soil (Cornwall) and 10,347 mg chromium VI/kg soil (Scotland) (Smith et al, 1989). Chromium VI was detected in soil from a heavily contaminated area of the UK and accounted for between 10% and 29% of the total chromium measured (9,400 to 26,150 mg total chromium/kg soil) (EHD, 1991).…”