• biological soil crusts;
  • drought stress;
  • soil algae;
  • soil cyanobacteria;
  • tolerance physiology

Tolerance to drought stress in soil crust microorganisms is essential for exploiting suitable organisms for restoring soil. In this study, the responses to drought stress of two drought-tolerant species, a green alga and a cyanobacterium, were compared with those of two non-tolerant green algae. In response to drought stress, induced by treatment with polyethylene glycol, the intracellular proline levels increased and were associated with increases in malondialdehye, pigment contents, and enzyme activities such as superoxide dismutase (SOD) and peroxidase (POD). Our results suggest that tolerance to drought stress could be indicated by the intracellular levels of proline, SOD, and carotenoids. This study provides insights into the drought physiology of the photosynthetic microorganisms and suggests that Leptolyngbya boryana and Chlorella vulgaris are suitable pioneer organisms for soil restoration.