Abstract
Lichens, characterized by having photobionts, can live even in the drought environment. Photobiont cyanobacteria in thalli of Peltigera polydactylon harvested in Akita was studied morphologically especially about their distribution, showing the typical cyanobacterial absorption and emission spectra. During the drought stress condition, inactivation of PSII measured by PAM system was observed in intact thalli, but the PSII fluorescence increased and recovered after re-watered. Using pico-second time resolved spectrophotometer, the PSII fluorescence decayed much faster and excitation energy transfer within PSII was still observed in the dried thalli. Lifetime of PSII increased within 1 min after water-absorption. The gene encoding alpha-subunit of nitrogenase (nifD) was cloned from cyanobacterial symbionts isolated from two locations in Akita (Mt Takao and Lake Tazawa). The deduced NifD sequences were 97.8% identical to each other between two isolates, which were much more similar to the genes from Anabaena than those from Nostoc.
