xerotolerance

Xerotolerance is the ability of an organism to survive prolonged exposure to extreme dryness. It includes xerophiles, which require low water availability, and xerotolerant species that endure desiccation without preferring it. In biology, xerotolerance is studied under desiccation tolerance and anhydrobiosis.

Organisms resist water loss through several strategies. They accumulate compatible solutes such as trehalose, glycerol, and proline to stabilize proteins and membranes; express protective proteins such as LEA (late embryogenesis abundant) family members; and enhance antioxidant defenses. Some exhibit vitrification, forming a glass-like cytoplasm that immobilizes cellular components during drying. Membrane lipids can be adjusted for stability, and some species use protective coatings or repair mechanisms that activate upon rehydration.

Notable xerotolerant organisms include tardigrades, which can enter anhydrobiosis during extreme dryness, and certain nematodes that survive desiccation. Fungi such as xerophilic species in the Aspergillus glaucus group, and drought-tolerant lichens, also demonstrate desiccation tolerance. Plants known as resurrection species—such as Selaginella lepidophylla and Xerophyta spp.—and orthodox seeds can withstand drying to low moisture and resume growth when water becomes available.

Xerotolerance has practical implications for agriculture and biotechnology, including breeding drought resistance, preserving seeds and vaccines in dry form, and studying life in extreme environments. It also informs theories about survival strategies under climate change and on other planets.