Chromium uptake and transport in barley seedlings (Hordeum vulgare L.)

Abstract

Potassium chromate is more toxic to the growth of barley in solution culture than chromic chloride, though apparent uptake of the latter is much faster. Inhibitor studies indicate that CrO4 (2-) uptake is "active" whereas Cr(3+) uptake is passive, demonstrating that the two forms do not share a common uptake mechanism. Studies on the form of Cr inside root cells show that in plants fed CrO4 (2-) the Cr remains largely unchanged whereas in plants fed Cr(3+) a little CrO4 (2-) (0.5 per cent) is produced. This conversion is dependent on the presence of living material and is probably enzymatic. Chromate uptake follows Michaelis-Menten kinetics at low concentration and is competitively inhibited by sulphate. Transport of chromium up the root is very slow, accounting for the low levels of Cr in the shoots. Chromate is transported better than Cr(3+) though still to a very limited extent. These experiments provide a physiological basis for previous observations.

Literature review: Phytoaccumulation of chromium, uranium, and plutonium in plant systems

“…Chromium(VI) is more toxic than Cr (m) and is more easily transported inside the plant (Mortvedt and Giordano, 1975). Chromium(VI) uptake has been reported to occur by an active mechanism, whereas Cr(III) uptake is passive, indicating that the two forms do not share a common uptake mechanism (Skeffington et al, 1976). Once in the xylem, C1-04~-is more easily transported than Cr(III), presumably because the latter is bound by ion exchange on the vessel walls or precipitated as Cr(OH)3.…”

“…For example, Cr(VI) was reported to be more toxic to the growth of barley in solution culture than Cr(III) supplied as CrC13 (Skeffington et al, 1976). A problem of any study of this type is that the solubilities of Cr(VI) and Cr(III) are not comparable under the same conditions (McGrath, 1982).…”

Phytoextraction of Cr(VI) from soil using Portulaca oleracea

“…In such a situation, phytoextraction can remediate the land inexpensively and with low environmental impact (Alyazouri et al 2014) The earliest studies on the interaction of Cr(VI) with plants were on chromium uptake as a problem of crop and plant contamination, so they mostly involved food crops such as wheat, barley and oat (Shewry and Peterson 1974;Skeffington, Shewry, and Peterson 1976;McGrath 1982). More recent studies have investigated non crop plants in order to identify Cr(VI) accumulators.…”

Chromium-Containing Organic Fertilizers from Tanned Hides and Skins: A Review on Chemical, Environmental, Agronomical and Legislative Aspects

“…The two ions do not share a common uptake mechanism: the uptake of Cr(III) is largely a passive process, whereas the uptake of Cr(VI) is mediated by low affinity sulphate carriers, specific for the uptake of essential metals [29,30,33,34] and quickly converted to Cr(III) in roots by Fe(III) reductase enzymes [31].…”

“…However, once in the xylem, Cr moves more readily [26,29,33,34]: very little translocation of Cr to the shoot is expected to occur when plants are supplied with either form of Cr. In fact conversion of Cr(VI) to Cr(III) occurs in the roots where Cr(III) is the most predominant form: once Cr is transformed, translocation is very little, being Cr(III) a form with low solubility [26,31].…”