THE COMPONENTS OF DESICCATION TOLERANCE MECHANISMS IN BRYOPHYTES: THE OLD STORY HAS BEEN UPDATED

Abstract

Bryophytes are not primitive precursors of vascular plants, but the diverse and highly evolved representatives of an alternative adaptation strategy, some fascinating physiology of their own. Bryophytes and vascular plants operate at different scales in relation to gravity, surface tension, laminar boundary layer, transport processes in the ambient air. Scale therefore has major physiological consequences: in many ways, bryophytes function differently from vascular plants. They use water when it is available, and suspend metabolism when it is not. In the course of drying out and rehydrating, they must pass through the levels of water stress experienced by DT vascular plants. They only transiently face the problem of metabolizing under water stress. It is like a ’drought avoidance’ strategy in vascular plants. To understand the various physiological processes and stress responses of bryophytes comparing with higher plants’ reactions it is essential to know the actual water status of the bryophyte tissue. Substantial external capillary water is generally present, and its amount can vary widely without affecting cell water status, which can result in difficulties in expressing precise actual water content (WC). The knowledge of full-turgor WC is principal. Desiccation tolerance is partly constitutive, allowing survival of rapid drying, and employs an active rehydration-induced repair and recovery. Bryophytes are capable of effective