The effects of high levels of Hg on senescence, proline accumulation and stress enzymes activities of maize plants

Intact plants of Zea mays L. var. Colt were grown for eight days with different concentrations of Hg (0, 50, 100, 200 and 400 mM). When exposed to Hg stress, the maize plants suffered a decrease in plant growth and chlorophyll a and b contents in shoots. Hg levels increased with increasing Hg content in the medium, but was much higher in roots than in shoots. On the contrary, K content decreased both in the roots and shoots. An increase in proline contents was found in the whole plant with increasing Mg in the medium. Soluble proteins increased in shoots but decreased in roots, where Hg content may reach values 100 times higher than those of shoots. ME; increased peroxidase activities, but decreased amylase activities in shoots.