Responses of the lichen Ramalina menziesii Tayl. to ozone fumigations

Abstract

Tropospheric ozone (O₃) is a strong oxidant, and is known to have serious negative effects on forest health. Lichens have bccn used as biomonitors of the effects of air pollution on forest health for sulfur and nitrogen pollutants. However, effects of O₃ on lichens are not well understood, as past fumigation studies and community analyses produced conflicting results. We fumigated the lichen Ramalina menziesii Tay!. with three levels of O₃ (10, 60, and 120 ppb) in two-month long experiments, testing photosynthesis, respiration, chlorophyll content, pigment degradation, and cell membrane leakage in response to the treatments, In southern California, the high ozone pollution season coincides with the wann arid summers. Many of the O₃ fumigations conducted by others were located in climates with regular rainfall events. In our fumigations, we allowed the lichens to maintain ambient water status. We found that R. menziesii showed no signs of physiological decline in response to low and moderate levels of O₃ fumigations and an insignificant response in some parameters to 120 ppb fumigations. Several plant species have been shown to be good indicators of O₃ pollution, while community studies of lichens and ozone have shown that lichens are not. In our estimation, the lichen R. menziesii is not a good indicator species for O₃ pollution, possibly due to antioxidant activity protecting the plant portion of the thallus (the algal cells within the symbiosis).

Citation

Riddell, J; Nash, TH III; Padgett, P. 2010. Responses of the lichen Ramalina menziesii Tayl. To ozone fumigations. Bibliotheca Lichenologica 105: 113-123.