The Mechanisms Of Desiccation Tolerance In Developing Seeds
Desiccation tolerance is one of the most fundamental properties of seeds. It is acquired late in seed development and is considered necessary for the completion of the plant's life cycle, as an adaptive strategy to enable seed survival during storage or environmental stress, and to ensure better dissemination of the species. The role of water status in desiccated tissues and problems related to testing tolerance in seeds are reviewed. The molecular mechanisms of desiccation tolerance has received extensive consideration only during this past decade. There is a general consensus that desiccation tolerance involves the protection of cellular membranes from the deleterious effect of water removal and the resultant necessity to maintain the bilayer structure in the absence of an aqueous environment. Therefore, some aspects of desiccation-induced membrane injury are described. Several strategies for coping with cellular desiccation have been identified the presence of high amounts of non-reducing sugars, the efficiency of free radical-scavenging systems and the expression of desiccation- and/or ABA-regulated genes. These molecular mechanisms allowing cellular protection are reviewed together with their respective role in dessication tolerance. It is concluded that desiccation tolerance is not likely to be ascribed to a single mechanism but rather to a multifactorial property in which each component is equally critical.