Resurrection plants and the secrets of eternal leaf

Most higher plants possess a phase in their life cycle in which tissues can survive desiccation. However, this is restricted to specialized tissues such as seeds and pollen. Resurrection plants are remarkable in that they can tolerate almost complete water loss in their vegetative tissues. The desiccated plant can remain alive in the dried state for several years. However, upon watering the plants rehydrate and are fully functional within 48 h. Underpinning this amazing ability is the capacity to accumulate large amounts of sucrose in the tissues. This sugar has the property of stabilizing enzymes and cellular structures in the absence of water. The sources of carbon that fuel sucrose synthesis are not known, but temporary carbohydrate stores and photosynthesis are the most likely candidates. On rewatering, the sucrose is metabolized rapidly as the tissues rehydrate. Increased expression of a number of genes in response to drought stress have been noted. A number of these are associated with metabolic pathways linked with primary carbohydrate metabolism. However, some genes related to LEA (Late Embryogenic Abundant) proteins have been isolated which suggests they too may play a role in maintaining tissue integrity during desiccation. How these mechanisms are integrated to enable resurrection plants to survive desiccation is discussed