PHYSIOLOGICAL-RESPONSES OF THE LICHEN RAMALINA-MENZIESII TAYL TO THE LOS-ANGELES URBAN-ENVIRONMENT

In southern California the lichen Ramalina menziesii was transplanted from a control area to a polluted area for three periods during a year. Net photosynthetic rates, recorded under standard conditions in the laboratory, chlorophyll contents and per cent phaeophytins were measured at 2-week intervals for samples from both sites. During summer periods at the polluted site chlorophylls and net photosynthesis declined substantially and per cent phaeophytins increased, but during the winter period no changes in these parameters were observed. At the control site little or no change in these parameters was observed during the transplant periods. During the winter there was no difference in net photosynthesis for samples collected from the two sites. During the summers the decline in the lichen at the polluted site was associated with the accumulation of 23 ions. Although not demonstrably toxic, nitrate concentrations alone explained over 75% of the variation of each physiological parameter. Fluoride was the second most important variable and it was probably accumulated to toxic levels.