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 constitutional) were studied in terms of possible relationship among Pb-tolerance and tolerance to Ca-, Mg- and P-deficits, general nutrient stress and the respective Ca-, Mg- and P-status of the plants. Plants were grown in a growth chamber in solution cultures containing 5, 10 or 20 mg Pb dm(-3). Both Silene populations were more Pb-tolerant than Biscutella Root lead concentrations in all plants were several times higher than 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 high tolerance to calcium deficit. These features of calcium metabolism are characteristic of this species and were not found in the Biscutella populations, which indicates that it did not evolve with the development of inducible tolerance to lead. The possible role of calcium in lead tolerance is discussed.