EN
This study addresses what underlies the high tolerance of some plant species to lead. The tolerance to lead of six species differing in their water requirements (xerophytes, mesophytes and hydrophytes) was determined. Seedlings were treated with lead (2.5 mg/dm3 Pb2+ from PbCl2) for 8 days in a hydroponic culture. Tolerance to lead (on the basis of root growth, i.e., index of tolerance), lead concentration in tissues and lead transport to stems (using AAS) were studied. The presence of lead in organs, tissues and cells was determined by the rhodizonate method. Using the results, we classified the tested plant species according to lead tolerance, in the following order: Berteroa incana < Helichrysum sp. < Leontodón hispidus < Cucumus sativus < Dianthus carthusianorum < Rumex aquaticus. The lead tolerance of these species correlated with their water requirements. Plants from dry stands demonstrated the lowest tolerance to lead (Berteroa incana IT = 10%, Helichrysum sp. IT = 15%), those from damp stands had higher tolerance, and those from wet stands had the highest (Rumex aquaticus IT = 60%). This dependence was corroborated by field observations showing that mesophyte species dominate calamine waste heaps (55%) despite the drought conditions and strong insolation that prevail there.