Desiccation-tolerant plants in dry environments

摘要

The majority of terrestrial plants are unable to survive in very dry environments.However,a small group of plants,called 'resurrection' plants,are extremely desiccation-tolerant and are capable of losing more than 90% of the cellular water in vegetative tissues.Resurrection plants can remain dried in an anabiotic state for several years and,upon rehydration,are able to resume normal growth and metabolism within 24 h.Vegetative desiccation tolerance is thought to have evolved independently several times within the plant kingdom from mechanisms that allow reproductive organs to survive air-dryness.Resurrection plants synthesise a range of compounds,either constitutively or in response to dehydration,that protect various components of the cell wall from damage during desiccation and/ or rehydration.These include sugars and late embryogenesis abundant (LEA) proteins that are thought to act as osmoprotectants,and free radical-scavenging enzymes that limit the oxidative damage during dehydration.Changes in the cell wall composition during drying reduce the mechanical damage caused by the loss of water and the subsequent shrinking of the vacuole.These include an increase in expansin or cell wall-loosening activity during desiccation that enhances wall flexibility and promotes folding.