Lichen Growth Responses to Stress Induced by Automobile Exhaust Pollution
JAMES D. LAWREY 1 and
MASON E. HALE JR. 2
1 Biology Department, George Mason University, Fairfax, Virginia 22030
2 Department of Botany, Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560
Growth rates were significantly suppressed in juvenile thalli (less than 0.1 square millimeter in initial size) of the saxicolous lichen Pseudoparmelia baltimorensis from a Potomac River island with high atmospheric lead burden as compared to the case for a similar island with a lower lead burden. However, larger thalli showed no significant changes in growth response as a result of atmospheric pollution stress. Disruptions in lichen growth thus appear to affect life stages when growth is most rapid andfood reserves are low. Once a minimnum thallus size is attained, the stress tolerance of the lichen increases.
Submitted on December 21, 1978
Revised on February 2, 1979
