Ultrastructural Changes and Electrolyte Leakage from Ozone Fumigated Epiphytic Lichens

Abstract

The ultrastructure of lichens and leakage of electrolytes from them were studied to assess the effects of ozone on four epiphytes. Bryoria capillaris (Ach.) Brodo & Hawksw., Bryoria fuscescens (Gyelnik) Brodo & Hawksw., Hypogymnia physodes (L.) Nyl. and Usnea hirta (L.) Wigg. were fumigated with control (<10), 40, 150 and 300 ppb ozone in controlled growth chambers for 2 and 4 week periods. The ultrastructural results suggest a direct effect of O 3 on carbon assimilation and storage in these lichens. Both the high concentrations of ozone (150 ppb and 300 ppb) and longer exposure time significantly increased starch volume and electron opacity of the pyrenoid matrix in chloroplasts of U. hirta and B. capillaris . Furthermore, in U. hirta , cytoplasmic lipid droplets and the number of pyrenoglobuli in pyrenoids were significantly increased at higher ozone concentrations. B. fuscescens showed little response to ozone at the ultrastructural level. In both Bryoria species the potassium leakage, and in B. fuscescens the conductivity of leachate, decreased during 4 weeks fumigation with high concentrations (150 and 300 ppb) of ozone. In most lichens, the total concentration of K + was either unchanged or increased at 150 ppb O 3 , suggesting that no leaching due to membrane damage occurred, but K + uptake by the lichens tended to increase at the concentrations of O 3 used. Copyright 1997 Annals of Botany Company