Photosynthesis of micro algae is often inhibited by salt stress (Kirst, 1990). Such an inhibition may be explained by a decrease in PSII activity. Indeed, in the green microalgae, salt stress inhibits PSII activity in Dunaliella tertiolecta and Chlamydomonas reinhardtii that is associated with a state-2 transition (Gilmour et al., 1985, Endo et al., 1995). In the cyanobacteria, it has been suggested that the decreased PSII activity in salt-stressed cells is associated with the state-2 transition (Schubert et al., 1993; Schubert and Hagemann, 1990). It has been reported that salt stress significantly inhibit the maximal efficiency of PSII photochemistry in Spirulina platensis cells and this inhibition is.
