STUDIES ON THERMOPROTECTION INDUCED BY HEAVY-METAL IONS IN SPRING BARLEY SEEDLINGS

Barley seedlings (Hordeum vulgare L., cv. Fatran) were pretreated with various concentrations of five heavy metal ions (Zn, Cu, Fe, Mg, Mn) for 3 d. When the subsequent heat shock was administered for 2 h, the heavy metal ions had thermoprotective effect against the sub-lethal (4 0-degrees-C) and lethal (45-degrees-C) temperature stresses, which wer e otherwise lethal to control (water grown) seedlings, The effectivene ss of each of the heavy metal ions was different, the most effective b eing Cu. The level of protection provided by these heavy metal ions wa s dependent on both the time and the concentration that plants were ex posed to them. The greatest differences were recorded in the thermotol erance mediated by applied metal ions in die shoot and root cells. The rmotolerance was exhibited by both the shoot and root of pretreated se edlings, even though the heavy metal stresses were applied solely to t he roots.