IMPACT OF HEAVY-METALS ON WATER-LOSS FROM LICHEN THALLI

Water loss in lichen species Cladonia convoluta (Lam.) and C. rangifor mis (L.) Hoffm. after exposure to heavy-metal (Pb, Cu, or Zn) solution s, either as single compounds or in combination, have been studied in this laboratory, Water loss was reduced in Pb-treated C. convoluta, wh ereas in C. rangiformis it increased significantly with 10(-2) M Pb tr eatment. Water loss increased significantly (P = 0.05) after Cu treatm ent in C. convoluta but was significantly reduced (P = 0.05) in 10(-8) and 10(6) M CuCl2-treated C. rangiformis. Similarly, water loss incre ased in all Zn-treated thalli but was significantly decreased (P = 0.0 5) in 10(-8) Al treated C. rangiformis. A cumulative effect of Pb, Cu, and Zn was observed on water loss after uptake from mixed-metal solut ion, K+ efflux indicated the extent to which the plasma membrane prese nts an effective barrier to metal ion uptake. (C) 1997 Academic Press.