Application of N 2-Fixing Cyanobacteria Nostoc sp . SOA 31 to Hydroponically Grown Water Spinach ( Ipomoea aquatica L . )

Under hydroponic systems, plants are grown in soilless media in containers, such as plastic buckets, tubs, or tanks. Containers can be arranged vertically to save space. Due to their space efficiency, hydroponic farming systems have become increasingly popular in urban communities. Another attractive aspect of hydroponic farming is its cleanliness, because of the replacement of soil with a hydroponic growth medium, which is basically a liquid. Although hydroponic systems have advantages compared to soil systems, they still depend on a large volume of nutrient solution, or on frequent adjustment of the nutrient solution, to prevent nutrient uptake by plant roots from producing radical changes in the nutrient concentrations and pH of the medium (Taíz & Zeiger, 2010). There are many media for hydroponic farming. Commercial mediums, like the AB-mix medium, are widely used among hydroponic farmers. Another medium, lab-developed to demonstrate potential inorganic solutions for plant growth, is the Hoagland medium. Among the many nutrients contained in a hydroponic medium, nitrogen is the highest in concentration. Plants require nitrogen to build many cell components, including the photosynthetic enzyme of RuBisCo in their leaves. Therefore, nitrogen deficiency, in plants, rapidly leads to chlorosis, which later inhibits plant growth. Nitrogen is usually provided in the form of ammonium (NH4 +) or nitrate (NO3 -). The long-term industrial production of ammonium and nitrate creates environmental burdens, because the processes use a great deal of fossil-fuel energy. In order to reduce the consumption of fabricated ammonium and nitrate, environmentally friendly nitrogen suppliers, such as N2-fixation cyanobacteria, can be used as an alternative source of nitrogen. Nitrogen-fixing cyanobacteria are commonly found in soil (Choudhary, 2011; Deep, Bhattacharyya, & Nayak, 2013; Singh, Kunui, Minj, & Singh, 2014). ARTICLE INFO

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