the effects of different concentrations of cadmium on the growth rate and beta-carotene synthesis in unicellular green algae dunaliella salina

the individual effects of cadmium concentrations (0, 0.005, 0.05and 0.5 mg. l-1) on the growth(cell number and chlorophyll content) and beta-carotene synthesis of two strains (iranian and australian) ofgreen algae d.salina have been studied for a duration of 36 days. the effects of these cadmiumconcentrations on the amount of cell magnesium and calcium have also been evaluated. an increase incadmium concentration resulted in a significant reduction in the cell number and chlorophyll content of d.salina. in comparison with control, in both strains, the increase of beta-carotene content of cells was observedin the first few days of the experiment, moreover, the amount of magnesium and calcium in cells decreased.the results indicated that the addition of 0.5 mg. l-1 of cadmium in the medium results in a 50 percentreduction in cell number after 96h. the decrease in growth rate and the increase in beta-carotene content ofcells is probably due to the formation of free radicals and deficiency of essential elements such as magnesiumand calcium, which is caused by high concentrations of cadmium in the medium.