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. andUsnea 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 O3on 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 ofU. hirtaandB. capillaris. Furthermore, inU. hirta, cytoplasmic lipid droplets and the number of pyrenoglobuli in pyrenoids were significantly increased at higher ozone concentrations.B. fuscescensshowed little response to ozone at the ultrastructural level. In bothBryoriaspecies the potassium leakage, and inB. fuscescensthe 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 O3, suggesting that no leaching due to membrane damage occurred, but K+uptake by the lichens tended to increase at the concentrations of O3used.