Abstract
Poikilohydric desiccation tolerant photosynthetic organisms are distributed among cyanobacteria, algae, mosses, ferns, and lichens. We have studied changes in photosynthetic activities during dehydration and rehydration processes in a terrestrial cyanobacterium, Nostoc commune, and in several mosses. The results indicated that, on dehydration, they deactivated photosynthetic activities and transfered the light energy absorbed by photosystem (PS) II to heat.
Here, we will report on responses of lichens to desiccation in comparison with those in N. commune and mosses. Responses of Trentepohlia aurea and cultured Trebouxia, which are photobionts, to dehydration will also be reported. The water loss during air drying and recovery of photosynthetic activities on rehydration were very rapid. On dehydration, specific deactivation of PSII and dissipation of light energy absorbed by PSII were observed. Measurements of water potential etc. showed that the osmolarity of the cells corresponded to around 1.0 M sorbitol.
