Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: May 25, 2007
Publication Date: November 1, 2008
Citation: Oliver, M.J. 2008. Biochemical and Molecular Mechanisms of Desiccation Tolerance in Bryophytes. In: Goffinet, B., Shaw, J., editors. Bryophyte Biology. 2nd Edition. New York, NY: Cambridge University Press. p. 269-298. Technical Abstract: Bryophytes, because they descend from the earliest branching events in the phylogeny of land plants, hold an important position in our investigations into the mechanisms by which plants respond to dehydration and by what paths such mechanisms have evolved. This is true regardless of what aspect of plant responses to dehydration one is interested in; whether it be mild water deficit stress as seen in most plants including those of agronomic importance, or desiccation as seen in orthodox seeds or in the leaves of desiccation-tolerant (or resurrection) plants. It is quite possible that the mechanisms by which bryophytes tolerate dehydration closely reflect the way the first land plants coped with the rigors of a drying atmosphere as they began their colonization of the land. It is believed that primitive plants spent much of their time in the air-dried state, which generally means they would experience water deficits of -100MPa or more. To survive such water deficits (most modern day plants do not survive -3 to -5MPa) these plants had to evolve vegetative desiccation tolerance. Given that, as we believe, desiccation tolerance first evolved in spores as a means of surviving the rigors of dispersal, it is quite likely that the type of desiccation tolerance that these early land plants exhibited was co-opted for use in vegetative cells (Oliver et al. 2005). As plants evolved to fill the multitude of different types of habitats and environmental niches that dry land offered, the ways in which plants were able to tolerate dehydration also evolved from a simple protective mechanism to ones of greater complexity and efficiency. It is clear, however, that as plants became more complex and gained the capability to transport water and nutrients through specialized conduits or vascular tissues, they lost the ability to tolerate desiccation of their vegetative tissues (Oliver et al. 2000). Bryophytes, whose ancestors marked the transition to land and hence preceded the development of tracheophytes in the land plant phylogeny, present a unique opportunity to look at mechanisms of dehydration tolerance, in particular vegetative desiccation tolerance, that have directly evolved from the earliest stages of land plant evolution. This chapter describes and discusses what we know of the cellular, molecular and biochemical aspects of desiccation tolerance in bryophytes and how it relates to their biology.