NEET AIPMT SOLVED PAPER SCREENING 2008

  • 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 reservior of nitrogen. Molecular nitrogen cannot be utilized directly by plants. It has to be fixed or converted into compounds prior to utilization. Symbiotic nitrogen fixation is accomplished by Khizobium 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 (AZnus 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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