Abstract

Relative water content and photosynthesis were measured after treating two liverworts, the highly drought-resistant Porella platyphylla (L.) Lindb, and the non-resistant Scapania undulata (L.) Dum., at 96.5% RH for various periods., In both species the variation in the relative water content during water stress followed the same pattern, dropping steadily up to 50 hr and then remaining unchanged. Photosynthesis reached a peak during the initial phase of water loss and decreased steadily with further water loss in both species. The maximum photosynthesis occurred after 2 hr of desiccation in Porella and after 6 hr in Scapania.