Uptake of Carrier-free Cs by Ramalina reticulata.

The uptake of carrier-free (137)Cs by Ramalina reticulata Kremp. does not appear to be directly linked to metabolism. The results indicate the presence of a barrier to entry of (137)Cs. The barrier is stabilized by Ca ions. Removal of Ca by pretreatment of the tissue in monovalent salt solutions increases the uptake of (137)Cs. Uptake under anaerobiosis is also greater than normal, but in this case, Ca displaced from the barrier membrane is not lost from the tissue and normal permeability is rapidly re-established when aerobic conditions are restored. Under anaerobiosis Ca(2+) increases damage to the respiratory mechanism presumably by increasing retention of toxic products.