Tungsten bioavailability and toxicity in sunflowers (Helianthus annuus L.)
D.R. Johnson, L.S. Inouye, A.J. Bednar, J.U. Clarke, L.E. Winfield, R.E. Boyd, C.Y. Ang and Jennifer Goss

Tungsten (W) metal is used in an increasing number of industrial and consumer applications, from electronics to munitions. Tungsten is taken up by plants in natural soils, yet a limited number of studies have been conducted on plant responses to high soil concentrations of tungsten due to anthropogenic activities. This study was conducted to examine tungsten bioavailability and toxicity in sunflower, Helianthus annuus L. Sunflowers were grown for 14 days in tungsten-spiked Grenada–Loring field soil that had been aged for six months. Sunflower total weight was significantly reduced at tungsten soil concentrations greater than or equal to 2600 mg kg–1, with leaf, stem, and root weights significantly reduced at concentrations greater than or equal to 2600, 325, and 3900 mg kg–1, respectively. Sunflower root and shoot length was also significantly reduced after exposure to tungsten levels greater than or equal to 3900 mg kg–1. Photosynthetic pigments chlorophyll a and carotenoids were significantly increased at greater than or equal to 3900 mg kg–1, while chlorophyll b was unaffected. Tungsten was bioaccumulated in both sunflower roots and leaves in a dose-dependent manner, with roots having a bioaccumulation factor of approximately two-fold from soil to plant tissue. Furthermore, sunflowers showed differential bioaccumulation of tungsten species in leaves, stems and roots, based on tungsten soil concentrations. In conclusion, sunflower may be a useful phytoremediation plant for soils with tungsten levels below 2600 mg W kg–1.

Key words: bioaccumulation, metal speciation, plant, soil, sunflower, tungsten

Land Contamination & Reclamation, 17 (1), pp. 141-151 (2009)

DOI 10.2462/09670513.939

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Article code 939