SOME PHYSIOLOGICAL STUDIES ON GREEN AND BLUE-GREEN ALGAE

Abstract

The present study aims at monitoring the effects of three light intensities degree (50, 100 and 150 μE 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 μE m-2 s-1. In respect to the photosynthetic rate, the highest gross photosynthesis was recorded at 100 μE m-2 s-1. Additionally, the highest activity of nitrogenase of Anabaena sp. was recorded at 100 μE m-2 s-1. The gross photosynthesis, net photosynthesis and respiration rate were superior at 100 μE m-2 s-1. Cultivation of both Chlorella sp. and Anabaena sp. isolates with growth regulators positively increased growth rate, biomass yield, lipids accumulation and concentration of pigments. Regarding Chlorella sp., TDZ at 1 ppm was best recommended for biomass yield, total chlorophyll and chlorophyll-a while TDZ at 3 ppm was the best for chlorophyll-b and carotenoids. In addition, TDZ at 5 ppm was superior for lipids content. Regarding Anabaena sp., TDZ at 5 ppm was best recommended for biomass yield, total chlorophyll and chlorophyll-a while TDZ at 1 ppm was the best for both of carotenoids and lipids content. Additionally, nitrogenase activity was superior at 1 ppm BA. Photosynthetic rate for both isolates was maximum at the lowest concentration of BA. Cultivation of Chlorella sp. and Anabaena sp. according to the optimum treatments of light intensity and growth regulators as indicated above, did successfully meet the needs for achieving high economic importance of Chlorella sp. and Anabaena sp. to be used in production of biofuel, natural colorants and biofertilizers in addition to organic matter that enhance soil fertility and crop productivity. Key words: Chlorella, Anabaena, growth regulators, nitrogenase, light intensity