Patterns of desiccation tolerance and recovery in bryophytes

The study of desiccation tolerance in bryophytes avoids the complications of higher-plant vascular systems and complex leaf structures. but remains a multifaceted problem. Some of the pertinent questions have at least partial analogues in seed biology - events during a drying-rewetting cycle with processes in seed maturation and germination, and the gradual loss of viability on prolonged desiccation, and the relation of this to intensity of desiccation and temperature, with parallel questions in seed storage. Past research on bryophyte desiccation tolerance is briefly reviewed. Evidence is presented from chlorophyll-fluorescence measurements and experiments with metabolic inhibitors that recovery of photosynthesis in bryophytes following desiccation depends mainly on rapid reactivation of pre-existing structures and involves only limited de novo protein synthesis. Following initial recovery, protein synthesis is demonstrably essential to the maintenance of photosynthetic function in the light, but the rate of maintenance turnover in the dark appears to be slow. Factors leading to long-term desiccation damage are diverse; indications are that desiccation tolerant species often survive best in the range -100 to -200 MPa.