| Research Abstract |
1. In addition to the previous culture stock, lichens were collected from Bonnin Island, Hawaii, Finland, Sweden, and Germany. From these lichen thallus, cultured tissues (ca 150 strains) were induced and have been maintained in several incubators in the laboratory. 2. Lichen thalli were intended to reform from cultured tissues. The condition of the thallus reforming include : poor nutrition (2-3 % water agar medium), moderate temperature (15ﾟC-18ﾟC), and lighting (ca. 2000 lux with a daily cycle). 3. The developmental stages of the thallus formation were investigated in detail in Peltigera praetextata. 4. Among 12 species of Peltigera, 6 species reformed their thallus in vitro. (4) The cyanobacterial morphotype of peltigera aphthosa, which are not common in nature, was obtained under wet conditions, and its chimeroid associations with green algal morphotype were obtained under dry conditions. 5. Same chemical substances were detected in both the natural green algal morphotype of Peltigera aphthosa and its cyanobacterial morphotype in vitro. (6) In the cultured Usnea hirta, the content of usnic acid was increased according to the thallus formation. (7) The mycobiont of Usnea hirta formed the similar thallus of natural parent lichens. (8) Based on our culture works a lichen can be considered as a special ecosystem of a fungus with green algae or cyanobacteria. (9) Cell aggregates of cultured lichens often produce different chemical substances from those of naturally occurred lichens. To investigate chemical substances of cultured lichens, the thallus of naturally occurred lichens were critically studied and found several minor substances, which were not reported previously. (10) Isolated mycobionts were furnished to other cooperative researchers, who have studied lichen physiology (photosynthesis), biochemistry (molecular studies of cytochrome), and applied fields (the effect of tyrosinase inhibition to human skin, ect.).
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