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Abstract
The present study aims at monitoring the effects of three light intensities degree (50, 100 and 150 æE m-2 s-1) and three types of growth regulators (BA, TDZ and KIN) at three concentrations (1, 3 and 5 ppm) for 28 days of incubation period on growth, development and some physiological characters of Chlorella sp. and Anabaena sp. isolates in addition to the N2-fixation ability of the Anabaena sp. isolate in an attempt to increase their economic importance to be used in many life fields. Upon weekly measurement of biomass yield, concentration of photosynthetic pigments and lipids accumulation of both Chlorella sp. and Anabaena sp. isolates in respect to the different degrees of light intensity, a significantly positive correlation was recorded between biomass yield and increased light intensity. However, the highest levels of light intensity were inductive for lipids accumulation but suppressive for concentrations of all photosynthetic pigments where their maximum values were obtained at 50 æE m-2 s-1. In respect to the photosynthetic rate, the highest gross photosynthesis was recorded at 100 æE m-2 s-1. Additionally, the highest activity of nitrogenase of Anabaena sp. was recorded at 100 æE m-2 s-1. The gross photosynthesis, net photosynthesis and respiration rate were superior at 100 æE m-2 s-1.