BHU PMT BHU PMT (Screening) Solved Paper-2010

  • question_answer
    Nitrogen-fixation in root nodules of Alnus is brought about by

    A)  Bradyrhizobium              

    B)  Clostridium

    C)  Frankia                               

    D)  Azorhizobium

    Correct Answer: C

    Solution :

                     Nitrogen is the most critical element. Atmosphere is the greatest reservoir of nitrogen. Molecular nitrogen cannot be utilized directly by plants. It has to be fixed or convened into compounds prior to utilisation. Symbiotic nitrogen fixation is accomplished by Rhizobium species, which occurs on the roots of leguminous plants. Certain non-leguminous plants also form nodules to fix nitrogen. The best known example in temperate region is alder (Ainus sp.). The bacteria involved in nodule formation is an Actinomycetes, the Frankia. Clostridium   is   anaerobic,   saprotrophic, free-living nitrogen fixing bacteria. Bradyrhizobium is symbiont in plants of Parasponia and soybean. The Azorhizobium forms both stem and root nodules in Sesbania (aquatic plant).


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