Abstract As nitrogen source is a necessary element in structure and cell metabolism, studying of nitrogen source and its effect on growth and different behave of photosynthetic organisms has received much attention. In this study, the comparative effects of three nitrogen sources (KNO3, NH4Cl and KNO3+NH4Cl) have been studied on physiological properties of two Dunaliella species, as Dunaliella sp. isolated from Gave-Khooni salt marsh and D.bardawil-UTEX2538, in different salt concentrations (0.1, 0.5 and 3 M NaCl) and cell division, changes in Chl a, Chl b, total Chl, total carotenoid total protein and fresh weight of the cells has been assayed during 24 days. D. bardawil had higher rates in cell growth, and in both strains the highest growth rates were observed at 0.5 M, treated with KNO3.Most of decreases in the amount of measured substances were happened on 8th day of assays and increases in Chl a, Chl b and total Chl contents were occurred in higher salt concentrations (0.5 M and 3 M) treated with KNO3. The cells in 0.5 M had the least fresh weight with the highest cell division rate. In D. bardawil, NH4Cl caused decrease in growth only in 0.1 and 3 M on 8th day. But noticeable decreases in Chl a, Chl b, total Chl, beta carotene and total carotenoid along with an increase in protein amount in both strains were observed only in 3M. After decreases on 8th day, the amount of assayed substances, increased at 3M. KNO3+NH4Cl as nitrogen source improved cell condition compared to cells treated with NH4Cl. D. bardawil responded to nitrogen source more different from other species and some increases in pigment contents occurred on 16th day. Overall, these results suggest that, NH4Cl make both species more sensitive to higher salt concentrations and after a short period of responses with decreased amount of pigments and arises in protein content, some increases could be a sign for coping with the new condition.

Keywords: Ammonium source, Dunaliella, Nitrate source, Pigment, Protein, Salt

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