Oxidative stress and ascorbic acid contents in Parmotrema reticulatum and Parmelia sulcata thalli

Paraquat-treatment of Parmotrema reticulatum and high light levels in the habitat of Parmelia sulcata can cause oxidative stress, which promotes an increase in ascorbic acid contents of thalli. Ascorbic acid was measured by an HPLC method. In P. reticulatum the increase was more pronounced in summer than in other seasons. In P. sulcata, thalli growing in sun-exposed habitats showed a higher ascorbic acid content than shade-growing specimens. (C) 1999 The British Lichen Society.