Root and shoot elongation as an assessment of heavy metal toxicity and 'Zn Equivalent Value' of edible crops

Y. H. Cheung*, Ming Hung WONG, N. F.Y. Tam

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

29 Citations (Scopus)


Seeds of thirteen edible plant species were tested for their response to heavy metals during their early development. It was found that a short-term root elongation test of six days could be used to evaluate the degree of toxicity of aqueous samples containing heavy metals. Shoot elongation was found to be less sensitive to metals than root elongation. The seeds were sown in pots containing freshwater sand to which known concentrations of metal solutions were added. The relative toxicity of the three metals, copper, nickel and zinc, followed the pattern of Ni > Cu > Zn. Results on the relative toxicity of Zn : Cu: Ni to various plant species indicated that the ratios were species-specific. The Zn equivalent concept of Zn : Cu : Ni = 1 : 2 : 8 could not be applied to all the plant species tested. The root growth of seeds of Brassica parachinensis (flowering Chinese cabbage) placed on filter papers in petri dishes to which metal solutions were added were tested. The sensitivity ranking of the metals tested was found to be as follows: Ni > Cd > Cu > Al > Fe > Zn > Pb > Mn > Ag. There was no significant difference (p > 0.05) in percentage reduction in root elongation among the four different repeated trials.

Original languageEnglish
Pages (from-to)377-383
Number of pages7
Issue number1
Publication statusPublished - Dec 1989

Scopus Subject Areas

  • Aquatic Science

User-Defined Keywords

  • edible crops
  • heavy metal toxicity
  • root growth inhibition
  • seed development
  • Zinc Equivalent Value


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