الفهرس 
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Abstract
ABSTRACT Biofertilizers are substances that contain living microorganisms such as microalgae which contain high levels of macronutrients and micronutrients when applied to seeds, plant surfaces, or soil, colonizes the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant through biological process such as nitrogen fixation and solubilization of rock phosphate. The major goal of the study to isolate and identify different microalgal species and investigating their growth potential using different nutrient media then selecting the best one support the maximum growth production for all the tested microalgae, and investigating the biochemical composition for the tested microalgal to explore the possible role of these isolates as biofertilizer for Phaseolus vulgaris growth. The test microalgae species (Chlorella vulgaris, Scendesmus dimorphus and Spirulina platensis) contain some biological active compounds like protein, carbohydrate, lipid, pigment, phytohormones that led to enhance growth and metabolism as well as yield of Phaseolus vulgaris plant. Thus, foliar spray application of biochemical organic substances, that can supply both macro and micronutrients, is one of the most innovative agricultural practices, as they have the advantage that they are safe to the environment, increasing the agricultural sustainability. Moreover, microalgae biomass showed to contain micro- and macronutrients, especially N, phosphorous (P), and K, and might be considered as an organic slow-release fertilizer. The use of these microalgal species in combination with chemical fertilizer was more effective than the use of biofertilizer only. The obtained results of the present study reported that treatment T6 (plant in soil with chemical fertilizer (N urea), foliar spraying with Chlorella vulgaris) was the most effective treatment led to improving the yield production and growth of common bean with minimizing the amount of NPK chemical fertilizers. During this study, the obtained results were summarized in the following items: 1- three different microalgae species were isolated and identified namely Chlorella vulgaris, Spirulina platensis and Scenedesmus dimorphus. 2- Three different nutrient media namely BG11, modified Navicula medium, and bold basal medium were chosen to study their effect on growth of the test microalgae, the experimental results indicated that modified Navicula medium supported relatively the highest growth of all the test microalgae. Hence, this medium was chosen for further growth experiments. 3- The dry weight of Spirulina platensis was employed as growth parameter and the highest growth maintained at day 15). While, for Chlorella vulgaris and Scenedesmus dimorphus biomass was harvested every day and the cell count was employed as growth parameters; the highest growth maintained at the end of the 6th day. 4- Microalgae contain high levels of lipid, carbohydrate, proteins, phytohormones and photosynthetic pigments. 5- The data recorded at vegetative and flowering stages of Phaseolus vulgaris growth indicated that, the determined growth parameters (shoot length /, fresh weight of shoot/, dry weight of shoot/plant, relative water content, number of leaves, root length, number of nodules, fresh weight of root/, dry weight of root/plant) and photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoids and consequently total pigments) as well as carbohydrates content (total soluble sugars, polysaccharides and total carbohydrates) and total protein content were increased due to the effect of all treatments compared to control T1. Meanwhile, T6 exhibited the highest values of the previous parameters. 6- Concerning the attributes of Phaseolus vulgaris yield seeds under the used treatments, the data recorded for shoot length/, shoot fresh and dry weight/, root length/, root fresh and dry weight/, number of pods/, number of seeds /, fresh and dry weight of pods, relative water content show a general increase in response to all treatments compared to control (T1). Also, T6 exhibited the highest values of the previous parameters. 7- Regarding the biochemical aspects of the yielded Phaseolus vulgaris seeds, total protein and carbohydrates content (total soluble sugars, polysaccharides and total carbohydrates) increase in response to all treatments compared to control. T6 exhibited the highest values of the previous parameters.