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THE OXYGEN TENSION WITHIN LICHEN THALLI
Author(s) -
MILLBANK J.W.
Publication year - 1977
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1977.tb02249.x
Subject(s) - lichen , thallus , darkness , botany , biology , nitrogenase , light intensity , nitrogen fixation , bacteria , physics , genetics , optics
SUMMARY A technique is described for estimating the internal pO 2 of moisture saturated lichen thalli under conditions of known light intensity and temperature. The method is polarographic, using unprotected microelectrodes, with brief experimental periods. In lichens with the phycobiont forming a zone of the thallus (Peltigera canina, P. poly‐dactyla and P. aphthosa) the pO 2 in the algal zone is normally slightly hypoaerobic rising to aerobic in bright sunny conditions, and becoming substantially hypoaerobic (pO 2 = 1–1.5 × 10 4 Pa) in darkness. The pO 2 within external cephalodia of lichens which have them is more affected by light. P. aphthosa and Placopsis gelida were examined and showed large and abrupt responses to changes in light intensity, the pO 2 ranging from 3 × 10 4 Pa to 10 4 Pa in Peltigera aphthosa; 2.1 × 10 4 Pa to 10 4 Pa in Placopsis gelida. The nitrogenase activity shown by these lichens is probably due to the high proportion of heterocysts, conferring some immunity to high pO 2 conditions.