Recovery of cowpea seedling roots from exposure to toxic concentrations of trace metals

• Published in: Plant and soil 2011-04, Vol.341 (1-2), p.423-436
• Main Authors: Blamey, F. P. C, Kopittke, P. M, Wehr, J. B, Menzies, N. W
• Format: Article
• Language: English
• Subjects: Acid soils; Agronomy. Soil science and plant productions; Aluminum; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; Copper; cowpeas; Degassing of metals; Ecology; Exposure; Fundamental and applied biological sciences. Psychology; gadolinium; gallium; General agronomy. Plant production; indium; lanthanum; Life Sciences; Mercury; Metal concentrations; Metals; Microscopy; Plant Physiology; Plant roots; Plant Sciences; Plants; Regrowth; Regular Article; Root growth; Roots; Rupture; ruthenium; scandium; Seedlings; Seeds; Soil; Soil pollution; Soil Science & Conservation; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Toxicity; Trace elements; Trace metals; Traumatic ruptures; Vigna unguiculata
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-010-0655-0

Rhizotoxic effects of many trace metals are known, but there is little information on recovery after exposure. Roots of 3-d-old cowpea (Vigna unguiculata (L.) Walp. cv. Caloona) seedlings were grown for 4 or 12 h in solutions of 960 μM Ca and 5 μM B at two concentrations (which reduce growth by 50 or 85%) of nine trace metals that rupture the outer layers of roots. Measured concentrations were 34 or 160 μM Al, 0.6 or 1.6 μM Cu, 2.2 or 8.5 μM Ga, 2.3 or 12 μM Gd, 0.8 or 1.9 μM Hg, 1.0 or 26 μM In, 2.4 or 7.3 μM La, 1.8 or 3.8 μM Ru, and 1.3 or 8.6 μM Sc. Roots were rinsed, transferred to solutions free of trace metals, and regrowth monitored for up to 48 h. Recovery from exposure to Hg occurred within 4 h, but regrowth was delayed for ≥ 12 h with Al, Ga, or Ru. There was poor regrowth after 4 or 12 h exposure to Cu, Gd, In, La, or Sc. Roots recovered after being grown for 12 to 48 h in 170 μM Al, 5.1 μM Ga, 2.0 μM Hg, or 1.4 μM Ru, but the extent of recovery was reduced with longer exposure time. Microscopy showed marked differences in symptoms on roots recovering from exposure to the various trace metals. Differences in (i) concentrations that are toxic, (ii) ability of roots to recover, (iii) time for recovery to occur, and (iv) symptoms that develop, suggest that each trace metal has a unique combination of rhizotoxic effects.