Effect of increasing concentrations of heavy metals on the growth of barley and wheat seedlings

The tolerance to increasing doses of lead and cadmium salts on the growth and survival of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) seedlings were studied. Seedlings grown under controlled conditions were treated with dilute (0.001-0.005 mM) solutions of either lead nitrate or cadmium bromide for 1, 4, or 7 days. Subsequently, they were incubated for 7 days in solutions of the same compounds, but at sublethal or lethal concentrations (0.05-10 mM). Plant pretreatment with low concentrations of heavy metals induced an increase in their tolerance to the metals, because pretreated plants could tolerate heavy metals at high concentrations. It is concluded that plant tolerance to increasing concentrations of heavy metals is related to the activation of protective and adaptive processes in their tissues.