Abstract
The effect of four heavy metals, including chromium, cadmium, lead and zinc were examined on germination, early seedling growth
and soluble phenol content of cowpea Vigna unguiculata. The final seed germination percentage was significantly reduced by most of
the heavy metals at 50ppm and 100ppm. Germination was suppressed by the metals in the order Cd> Cr> Pb> Zn. Both root and shoot
growth of the seedlings were reduced by all the heavy metals tested. TL 50 values for Cd, Cr, Pb and Zn were 53,07, 55.86, 70.75 and
81.24, respectively. As a stress response, the soluble phenol content was remarkably elevated by the heavy metals at concentrations of
50ppm and 100ppm. Phenol accumulation due to heavy metals stress occurred in the order Cd> Cr> Pb> Zn. The mechanisms
whereby heavy metals cause toxicity to plants are discussed.
