The effect of different molybdenum concentrations on the fixation of nitrogen of phaseolus vulgaris and vigna unguiculata
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Molybdenum is a micronutrient usually found in alkaline soils with high pH levels. Molybdenum also has a lot of compounds associated with it for example molybdenum sulphide and selenites, sodium molybdate in the anhydrous form calcium Molybdate, molyte and molybdic oxide. In the soil molybdenum exists predominantly in the form of the oxyanion molybdate which serves as an essential micronutrient in all kingdoms of life. Molybdate alone doesn’t exhibit biological activity but it is bound to an organic pterin backbone which upon binding of molybdate is converted to molybdenum cofactor. Molybdenum is a transition metal which occurs in the lithosphere at an average abundance of 1.2mg per kg of soil and represents one of the trace elements in the biological system.(Kaiser, Gridley, Ngaire Brady, Phillips, & Tyerman, 2005) Molybdenum also has the ability to withstand high temperatures and maintain strength under these conditions that are responsible for the fact that it finds most of its application at the elevated temperatures thus when exposed to temperatures in excess of 760 degrees Celsius in air, rapid oxidation occurs and the oxide layer sublimes and the base metal is attacked. Therefore, molybdenum performs best in inert vacuum environments. The leguminous plants have the greatest capability in fixing nitrogen through the symbiotic relationship and the well-known bacterium involved is the rhizobium bacterium.(Franche, Lindström, & Elmerich, 2009; Mendel & Hänsch, 2002). The bacterium infects the root nodules of leguminous plants where the fixation process takes place. After fixation, nitrogen within the soil is oxidized to nitrate by nitrite reductase and nitrate reductase. These enzymes are responsible for biological fixation of nitrogen within the soil system and they reside within the root nodules of legumes. Molybdenum is essential in metabolic functions of nitrate reductase and nitrogenase enzymes (Marschner,1995., Römheld & Marschner, 1991). Molybdenum as a cofactor in nitrogen fixation indirectly affects the crop biomass production by influencing nitrogen fixation for biomass production (Mendel & Hänsch, 2002).There is a linkage between Molybdenum concentration and nitrogen fixed by the plants, one method used to establish the concentration of molybdenum is to determine the amount of nitrogen assimilated by the cover crop biomass (Pramanik, Haque, Kim, & Kim, 2014). Such methods may include hairy growth and dry weight (Boddey & Knowles, 1987). Nitrogen exists as a diatomic molecule and contributes over 78% of the atmospheric air. Nitrogen in its stable state comprises of a triple bond that links the two nitrogen atoms. Nitrogen from the atmosphere has got to be introduced into the soil and eventually the biological system that involves the plants and the animals. However, Nitrogen is also obtained by the soil through: Direct application of fertilizers Lightening Biological nitrogen fixation by the legumes The main pathway of biological nitrogen fixation is the one where all the emphasis is centered for improvement of the nitrogen uptake by the legumes. Biological nitrogen fixation: It is a process in which nitrogen from the atmosphere is incorporated into the tissue of certain plants. That is to say only certain group of plants are able to fix nitrogen in this way for example the forage plants which include the legumes.