Impact of Heavy Metals on Water Loss from Lichen Thalli

Water loss in lichen speciesCladonia convoluta(Lam.) andC. rangiformis(L.) Hoffm. after exposure to heavy-metal (Pb, Cu, or Zn) solutions, either as single compounds or in combination, have been studied in this laboratory. Water loss was reduced in Pb-treatedC. convoluta,whereas inC. rangiformisit increased significantly with 10−2MPb treatment. Water loss increased significantly (P= 0.05) after Cu treatment inC. convolutabut was significantly reduced (P= 0.05) in 10−8and 10−6MCuCl2-treatedC. rangiformis.Similarly, water loss increased in all Zn-treated thalli but was significantly decreased (P= 0.05) in 10−8MtreatedC. rangiformis.A cumulative effect of Pb, Cu, and Zn was observed on water loss after uptake from mixed-metal solution. K+efflux indicated the extent to which the plasma membrane presents an effective barrier to metal ion uptake.