Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: May 20, 2007
Publication Date: October 1, 2007
Citation: Oliver, M.J. 2007. Lessons on dehydration tolerance from desiccation tolerant plants. In: Jenks, M., Wood, A., editors. Plant Desiccation Tolerance. Ames, IA:Wiley-Blackwell Publishing. p. 11-50. Technical Abstract: Extremophiles: organisms that thrive (a relative term) in environments where conditions are such that the majority of organisms cannot survive. This is not strictly true if one is describing desiccation-tolerant plants, as other plants do grow around them, but it is certainly true that they can survive levels of dehydration, or water-deficits, that the majority of plants cannot. Bewley, (1979) defined desiccation tolerance as the ability to “revive from the air-dry state (the air being of low relative humidity), and a plant which is desiccated is one from which all available water has been lost to the surrounding dry atmosphere.” In more precise terms we tend to define desiccation tolerance as the ability to equilibrate cellular water potential with that of moderately dry air and then resume metabolism and growth upon rehydration. Desiccation-tolerant plants all survive a minimum of -100 MPa and most much lower water deficits. The large disparity in the ranges of tolerance to dehydration in sensitive and desiccation-tolerant plants reveals a fundamental difference between drought tolerance in sensitive species and desiccation tolerance. Sensitive species, when soil moisture becomes limiting during a drought, utilize mechanisms to retain water and to limit the amount of dehydration to a level that can be endured over a relatively short period of time. More precisely put, sensitive plants attempt to “maintain a chronic disequilibrium between wet cells and dry air” (Alpert & Oliver, 2002) and when this strategy fails they die. Drought tolerance can be described as the relative ability a plant has to maintain the disequilibrium, limit dehydration to a non-injurious level, and, in agronomic terms, maintain productivity when soil water potentials are low. Desiccation-tolerant plants, however, react to low soil moisture and dry air by initiating mechanisms that prepare the vegetative cells for dehydration and do not attempt to maintain the chronic disequilibrium between wet cells and dry air. This chapter discusses what we have learned from desiccation tolerant plants in terms of the mechanisms and strategies that have evolved to prevent or repair dehydration damage in plants.