The present study was undertaken to investigate the influence of benzyladenine (BA) on growth and metabolism of the freshwater microalga Chlorella vulgaris cultures subjected to sodium chloride stress. The interactive effects of salinity (2, 5, and 15 ppt NaCl) and/or benzyladenine (BA, 10 ppm) on growth, pigments composition, carbohydrate constituents, protein content, amino acids concentrations, as well as the endogenous phytohormones levels of the fresh water microalga Chlorella vulgaris were investigated. Cell density, specific growth rate, biomass yield and pigments composition values were decreased with increasing salinization level, except for 2 ppt NaCl which significantly decreased the previously mentioned parameters. Metabolic constituents (carbohydrate fractions, protein contents and amino acids conistituents also had the same pattern of response. Increasing salinity decreased the endogenous levels of the growth promoters (Auxin "IAA", "Gibberellic acid" GA3 and cytokinins) and a significant increase in the growth inhibitor "abscisic acid" (ABA) was attained. Addition of BA improved the inhibitory effects of salinity and osmoregulate cell metabolism either by producing high contents of the low molecular weight molecules ("LMWM" amino acids, protein and soluble sugars) or enhancing growth promoting substances.
Key words: Microalgae, salinity, osmoregulation, phytohormones, benzyladenine, metabolism.
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