Effect of salt stress on growth, lipid peroxidation, antioxidant enzymes and phycobiliproteins in two species of Nostoc

The changes in growth, and content of proline, MDA and phycobiliproteins and the involvement of the antioxidant enzymes in relation to salt stress tolerance were investigated in Nostoc ellipsosporum and N. piscinale. Both microalgae were grown in BG-11 medium in the presence of various concentrations of NaCl (0, 50 100, 150, 200, and 250 mM) and. Both species showed an increase in dry weight under stress. N. ellipsosporum was more tolerant to NaCl stress than that of N. piscinale and N. ellipsosporum obtained more biomass under salinity stress in comparison to N. piscinale. Salt stress induced catalase (CAT), peroxides (POX), polyphenol oxidase (PPO) and superoxide dismutase (SOD) activities in N. ellipsosporum and N. piscinale after 9. Salinity treatment significantly induced increase in phycobiliprotein in N. piscinale and in N. ellipsosporum. This increase was prominent in N. ellipsosporum than that of N. piscinale. Moreover, the variability of phycobilisome size was also examined. The size of phycobilisomes can be usually represented by the ratio [PE + PC/APC]. The size of phycobilisomes (by elongation of the phycobilisome rods) increased significantly under salt stress.