Preliminary Studies of the Gross Photosynthetic Response of Lichens to Peroxyacetylnitrate Fumigations

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Abstract
Samples of Collema nigrescens (Huds.) DC., Hypogymnia enteromorpha (Ach.) Nyl. and Parmelia sulcata Tayl. were fumigated with peroxyacetylnitrate (PAN) daily for 4 h periods over 7-8 days at concentrations of 100 and 50 ppb. All of these species as well as Peltigera rufescens (Weis.) Humb. were fumigated for 1 h at 200 ppb PAN. Injury was evaluated as reduction in gross photosynthesis during the fumigation periods. Results of the long term, low concentration fumigations show that P. sulcata is more sensitive to PAN than H. enteromorpha and that C. nigrescens is apparently unaffected under the experimental conditions. Results of the acute high dose fumigation show slight enhancement of photosynthesis in all species except H. enteromorpha. With the exception of C. nigrescens, laboratory results are generally consistent with unpublished observations of distribution and vitality of the species in the field.