Viability of dried filaments, survivability and reproduction under water stress, and survivability following heat and UV exposure in Lyngbya martensiana, Oscillatoria agardhii, Nostoc calcicola, Hormidium fluitans, Spirogyra sp. and Vaucheria geminata

Dried vegetative filaments ofSpirogyra sp.,Vaucheria geminata andNostoc calcicola died within 1/2, 1 and 4 h, respectively; those ofHormidium fluitans, Oscillatoria agardhii andLyngbya martensiana retained under similar storage conditions viability for 3, 5 and 10 d, respectively. The viability of dried vegetative filaments ofL. martensiana, O. agardhii andH. fluitans decreased on storage at 20°C in the dark.L. martensiana andO. agardhii tolerated 0.8 mol/L NaCl. The resistance to desiccation inL. martensiana andO. agardhii exhibited similar dependence as that to frost, to heat and UV light.O. agardhii filaments became slightly broader and their cells developed large number of gas vacuoles when grown in 0.8 mol/L NaCl-containing medium. The water stress imposed on growing algae either on high-agar solid media or in NaCl-containing liquid media reduced hormogonium formation inL. martensiana andO. agardhii, heterocyst and akinete formation inN. calcicola and fragmentation inH. fluitans; it did not induce conjugation inSpirogyra sp. and formation of reproductive organs inV. geminata. In all studied algae the stress reduced at various levels the survival of vegetative parts. Generally, algal body form and composition rather than habitats seem to decide primarily the level of resistance against various stress conditions.