The Role of Calcium in the Stress Response of the Halotolerant Green Alga Dunaliella bardawil

Summary ISSA A. A. 1996. The role of calcium in the stress response of the halotolerant green alga Dunaliella bardawil BEN-AMOTZ et AVRON. - Phyton (Horn, Austria) 36 (2): 295-302, 1 figure. - . English with German summary. The effect of hypertonic shock on D. bardawil cells in the presence or absence of Ca2+ (1,5,10 mM) on cell volume and its metabolites were followed. When the Na+ concentration of the medium was increased from 0.5 M to 4 M, the volume of packed D. bardawil cells shrank (2 min.), followed by cell volume-regulation phase; in which the cells swell (1-2 h). In the presence of Ca2+, a slight recovery in the cell volume was observed by decreasing the uptake of ions (Na+ & Cl") in comparison to the cultures containing NaCl alone. Generally, Ca2+ has a positive role in the photosynthetic oxygen evolution and dark oxygen uptake in Dunaliella cells. Moreover, the intracellular glycerol contents of D. bardawil cells was sharply decreased whereas the carbohydrate content was increased by low concentrations of Ca2+ (1 & 5 mM).