Viability of dried cells, and survivability and reproduction under water stress, low light, heat, and UV exposure in Chlorella vulgaris

Abstract

Dried Chlorella vulgaris Beyerinck cells were 100% viable when stored in desiccators over fused CaCl₂ for 2 days either in light or dark, but the viability decreased to1% after 30 days at 20 C in light. Neither dried nor wet cells remained viable after10 days at 0 C in dark. Tolerance of C. vulgaris cells to dry storage might be dueeither to their unicellular nature or to the chemical composition of cell wall containing sporopollenin. Osmotic regulation did not seem to occur, as the alga was salt-sensitive. Autospores or young vegetative cells were more sensitive than autospore mother cells to both physical and physiological water stress, imposed respectively by growing them on media with a high agar content or in salinized liquid media. The rupture of autospore mother cells and release of autospores did not occur even in100 mM NaCl. The vegetative cells remained viable in darkness at 22 1 C for 45days, but the formation of autospore mother cells required light intensities of more than 10 mmol m² s¹. The vegetative cells were sensitive to heat or UV.