Uptake and speciation of vanadium in the rhizosphere soils of rape (Brassica juncea L.)

Abstract

The response of rape (Brassica juncea L.) to different vanadium (V) speciation in rhizosphere soils was investigated in pot experiments using an agricultural soil containing 147 mg V kg(-1) supplemented with 0-500 mg V kg(-1) of pentavalent V [V(V)] and a mining soil containing 774 mg V kg(-1). Tetravalent V [V(IV)] accounted for 76.1 and 85.9 % of total V in the untreated agricultural soil and mining soil, respectively. The proportion of both V(V) and water-extractable V increased with increasing concentrations of V(V) in the agricultural soil. The growth of rape substantially reduced the concentrations of V(V) but not V(IV) in the rhizosphere soil, suggesting that V(V) was actively involved in the soil-rape interaction of V. Both soil V(V) and water-extractable V were negatively related to the total rape biomass, but were positively correlated with the concentration of root V. No such relationships were found for total V and soil V(IV). Together, these results indicate that soil V(V) and water-extractable V might better reflect the toxicity of V in soils than total V and soil V(IV). Rape accumulated V in the sequence: roots > > stem > leaf > seed. As indicated by the remarkably low root bioconcentration factor of V(V) (0.41-7.24 %), rape had a lower ability to accumulate V than other plants reported in the literature (14.6-298 %). Only a small fraction of V in rape roots was translocated to the aboveground organs (the translocation factor was 3.57-46.9 %). No V was detectable in seeds in the soils at 147 and 197 mg V kg(-1), and no seed was produced in the soils at higher V concentrations. Thus, the risk of V intake by humans via the consumption of rapeseed-based foods under normal conditions is considered to be lower than that of other plants.

Vanadium: Global (bio)geochemistry

“…The mobile V in soils occurs mainly as V(V) and only minor amounts are present as V(IV) (Baken et al, 2012;Burke et al, 2012). Vanadate is also the most available form for plants (Tian et al, 2015). Although red mud, the fine sediment byproduct of bauxite processing, is not soil, a recent study provides insight into V mobilization from mineral solids.…”

Vanadium stimulates pepper plant growth and flowering, increases concentrations of amino acids, sugars and chlorophylls, and modifies nutrient concentrations

“…Vanadium (V) is a transition metal widely distributed in the Earth’s crust, where it may be found at a mean concentration of 20 to 120 mg kg -1 [ 1 ]; however, it has little mobility in soil, since less than 1% of the total V is extractable and leachable with water [ 2 , 3 ]. The first studies identified V as an element highly toxic to plants [ 4 ], which decreased interest in evaluating its effect on cultivated species.…”

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“…V is generally not very mobile in the soil, and it has several cationic states, including V 2+ , V 3+ , V 4+ , and V 5+ ; the latter form is characterized by being a strong oxidant (Matsugo et al, 2015). V 4+ is the predominant form in the soil, which is less mobile and toxic than the pentavalent (V 5+ ) form (Tian et al, 2015). Small amounts of V stimulate plant biomass production, whereas root and leaf growth inhibition and morphological changes have been reported with high levels of this element in Ipomoea aquatica (Chen et al, 2016 (Nalewajko et al, 1995).…”

“…forma se caracteriza por ser un oxidante fuerte (Matsugo et al, 2015). La forma predominante en el suelo es V 4+ , la cual es menos móvil y tóxica que la forma pentavalente (V 5+ ) (Tian et al, 2015). En plantas se ha reportado que pequeñas cantidades de V estimulan la producción de biomasa, mientras que niveles altos de este elemento inhiben el crecimiento y causan cambios morfológicos en hojas y raíz de Ipomoea aquatica (Chen et al, 2016 antocianinas (Schiavon et al, 2016).…”