THE ROLE OF METAL‐ION BINDING IN MODIFYING THE TOXIC EFFECTS OF SULPHUR DIOXIDE ON THE LICHEN UMBILICARIA MUHLENBERGII

Total ¹⁴ C fixation in Umbilicaria muhlenbergii was not significantly affected at levels near the capacity of the first binding site (c. 12 μmol g^-1 ) of class A metal ions or borderline metal ions with class A characteristics: i.e. Sr²⁺ , Mg²⁺ , Ca²⁺ , Ni²⁺ , and Zn²⁺ . Although both Cu²⁺ and Pb²⁺ are borderline ions with significant class B character, only Cu²⁺ greatly reduced fixation. However Ni²⁺ and Pb²⁺ , as well as Cu²⁺ , induced …