Comparative Impacts of Heavy Metals on Root Growth as Related to Their Specificity and Selectivity

Comparative Impacts of Heavy Metals on Root Growth as Related to Their Specificity and Selectivity Two-day-old maize (Zea mays L.) seedlings were incubated on the solutions of Ag, Cd, Pb, Zn, Cu, Tl, Co, and Hg salts (0.001 to 3 g/l). Toxicity of heavy metals was assessed as the inhibition of root growth on the first, second, and third days, the change in the length of the lateral root zone, and the duration of lateral root development from the first division in pericycle to emergence. For all salts under study, the ratio of the lethal concentration to the lowest concentration slowing down root growth was about ten, and growth inhibition was not almost enhanced in the course of three days. With concentrations calculated as g/l, metal toxicity declined in the following order: Cu ≈ Tl > Ag > Cd > Hg > Co > Zn > Pb; for molar concentrations, the order was the following: Tl3+ > Cu2+ > > Ag+ > Hg2+ ≈ Cd2+ > Zn2+ ≈ Pb2+ ≈ Co2+. Duration of lateral root development was least affected by heavy metals. Metal affinity of biological compounds for SH-groups was closely correlated (r = 0.9) with the molar concentration that inhibited primary root growth by 50%. Because of the narrow range of effective concentrations, only slightly increasing inhibition over the exposure time, tolerant root branching, and close relationship between the toxicity and the constant of binding to SH-groups, we conclude that the salts under study exert nonselective inhibition and root growth is slowed down due to the general toxicity of heavy metals rather than selective inhibition of any particular process or processes. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Russian Journal of Plant Physiology Springer Journals

Comparative Impacts of Heavy Metals on Root Growth as Related to Their Specificity and Selectivity

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Publisher
Kluwer Academic Publishers-Plenum Publishers
Copyright
Copyright © 2003 by MAIK “Nauka/Interperiodica”
Subject
Life Sciences; Plant Sciences
ISSN
1021-4437
eISSN
1608-3407
D.O.I.
10.1023/A:1023838707715
Publisher site
See Article on Publisher Site

Abstract

Two-day-old maize (Zea mays L.) seedlings were incubated on the solutions of Ag, Cd, Pb, Zn, Cu, Tl, Co, and Hg salts (0.001 to 3 g/l). Toxicity of heavy metals was assessed as the inhibition of root growth on the first, second, and third days, the change in the length of the lateral root zone, and the duration of lateral root development from the first division in pericycle to emergence. For all salts under study, the ratio of the lethal concentration to the lowest concentration slowing down root growth was about ten, and growth inhibition was not almost enhanced in the course of three days. With concentrations calculated as g/l, metal toxicity declined in the following order: Cu ≈ Tl > Ag > Cd > Hg > Co > Zn > Pb; for molar concentrations, the order was the following: Tl3+ > Cu2+ > > Ag+ > Hg2+ ≈ Cd2+ > Zn2+ ≈ Pb2+ ≈ Co2+. Duration of lateral root development was least affected by heavy metals. Metal affinity of biological compounds for SH-groups was closely correlated (r = 0.9) with the molar concentration that inhibited primary root growth by 50%. Because of the narrow range of effective concentrations, only slightly increasing inhibition over the exposure time, tolerant root branching, and close relationship between the toxicity and the constant of binding to SH-groups, we conclude that the salts under study exert nonselective inhibition and root growth is slowed down due to the general toxicity of heavy metals rather than selective inhibition of any particular process or processes.

Journal

Russian Journal of Plant PhysiologySpringer Journals

Published: Oct 17, 2004

References

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