Diverse algae possess the ability to recover from extreme desiccation without forming specialized resting structures. Green algal genera such as Tetradesmus (Sphaeropleales, Chlorophyceae) contain temperate terrestrial, desert, and aquatic species, providing an opportunity to compare physiological traits associated with the transition to land in closely related taxa. We subjected six species from distinct habitats to three
dehydration treatments varying in relative humidity (RH 5%, 65%, 80%) followed by short- and long-term
rehydration. We tested the capacity of the algae to recover from
dehydration using the effective quantum yield of
photosystem II as a proxy for physiological activity. The degree of recovery was dependent both on the habitat of origin and the
dehydration scenario, with terrestrial, but not aquatic, species recovering from
dehydration. Distinct strains of each species responded similarly to
dehydration and
rehydration, with the exception of one aquatic strain that recovered from the mildest
dehydration treatment. Cell ultrastructure was uniformly maintained in both aquatic and desert species during
dehydration and
rehydration, but staining with an amphiphilic styryl
dye indicated damage to the plasma membrane from osmotically induced water loss in the aquatic species. These analyses demonstrate that terrestrial Tetradesmus possess a vegetative desiccation tolerance phenotype, making these species ideal for comparative omics studies.