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Dessication Tolerance in Bryophytes and Lichens

Proctor, M.C.F. [1].

Time relations of bryophyte desiccation tolerance.

Time relations are important in bryophyte desiccation tolerance for two reasons. First, neither the cessation nor the recovery of metabolism through a wet-dry-wet cycle can be instantaneous; we know that the recovery processes take time. Second, desiccation tolerance and recovery must relate to dry and wet periods as they are presented under natural conditions in the field. We are accustomed to think in terms of long dry and wet periods (days, weeks, months). In fact, data-logging shows that a large proportion of both wet and dry periods are short - from a few hours down to an hour or less. Our understanding of bryophyte (and lichen) desiccation tolerance needs to encompass both these short-term fluctuations in water availability and (at least potentially) in water content, and the changing pattern of wet and dry periods round the year. Data will be presented on time-relations and rates of recovery recorded by chlorophyll fluorescence and infrared gas analysis in a range of species, and also on the lengths of wet and dry periods recorded in the field from a population of Grimmia pulvinata on a dry wall top in Devon, U.K., and from a cloud forest in the Venezuelan Andes. These will be considered in relation to the effect of storage of external capillary water by the bryophytes in bridging dry periods of varying length in different habitats. The results are a reminder that recovery from desiccation is a complex process involving many metabolic systems, which are likely to recover at different rates. Thus, 'recovery' that is adequate to maintain life through a period of frequent desiccation may not be adequate for completion of the life cycle. We need to study desiccation responses of a diversity of processs over a continuous range of time-scales from minutes and hours to seasons.


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1 - University of Exeter, Department of Biological Sciences, Washington Singer Laboratories, Perry Road, Exeter, EX4 4QG, United Kingdom

Keywords:
dessication
desiccation tolerance
brophytes
lichens.

Presentation Type: Symposium or Colloquium Presentation
Session: 35-9
Location: Salon K - Austin Grand Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 3:00 PM
Abstract ID:504


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