Experiments on the effect of different intensities of desiccation on bryophyte survival, using chlorophyll fluorescence as an index of recovery

Chlorophyll fluorescence provides a non-invasive and non-destructive method to follow various aspects of the photosynthetic function of bryophytes under relatively natural conditions, which is easy to use and can be applied to small amounts of material. Some of its potentialities (and potential pitfalls) for bryophyte desiccation physiology are outlined. Data are presented on the responses of eleven desiccation-tolerant bryophytes to drying at -41, -114, -218 and -412 MPa for periods up to similar to240 days. Recovery was assessed from F-V/F-M after 20 min and 24 h re-wetting, and from the mean F-M value after 24 h. For the more desiccation-tolerant species, Grimmia pulvinata, Syntrichia ruralis, Andreaea rothii, Racomitrium lanuginosum, R. aquaticum, Leucodon sciuroides, Pleurochaete squarrosa and Ulota crispa, long-term survival (>30-120 d) was generally best at similar to -100 to -200 MPa (20-45% r.h.). The moderately desiccation-tolerant Anomodon viticulosus, Porella platyphylla and P. obtusata survived best at the highest humidity used, -41 MPa (74% r.h.).