THE RELATIONSHIPS BETWEEN CONSTITUTIONAL AND INDUCIBLE PB-TOLERANCE AND TOLERANCE TO MINERAL DEFICITS IN BISCUTELLA-LAEVIGATA AND SILENE-INFLATA

Four populations, two each of Silene inflata and Biscutella laevigata, characterized by different tolerances to lead (inducible and constitu tional) were studied in terms of possible relationship among Pb-tolera nce and tolerance to Ca-, Mg- and P-deficits, general nutrient stress and the respective Ca-, Mg- and P-status of the plants. Plants were gr own in a growth chamber in solution cultures containing 5, 10 or 20 mg Pb dm(-3). Both Silene populations were more Pb-tolerant than Biscute lla Root lead concentrations in all plants were several times higher t han in shoots. Shoot lead concentrations were significantly higher in both Silene populations than in Biscutella. The high lead tolerance of the Silene populations was accompanied by their high Ca-status and hi gh tolerance to calcium deficit. These features of calcium metabolism are characteristic of this species and were not found in the Biscutell a populations, which indicates that it did not evolve with the develop ment of inducible tolerance to lead. The possible role of calcium in l ead tolerance is discussed.