Root and shoot elongation as an assessment of heavy metal toxicity and "Zn equivalent value' of edible crops

Seeds of 13 edible plant species were tested for their response to heavy metals during their early development. 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 less sensitive to metals than root elongation. Relative toxicity followed the pattern 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 (Chinese cabbage) placed on filter papters in petri dishes to which metal solutions were added were tested. Sensitivity ranking showed Ni > Cd > Cu > Al > Fe > Zn > Pb > Mn > Ag. -from Authors