Question

(i) Name the enzyme involved in nitrogen fixation by Rhizobium. 

(ii) Name the pigment seen in root nodules of leguminous plants and explain its role in nitrogen fixation.

(iii) Explain the two ways by which NH₄⁺ is used to synthesise amino acids in plants

Answer 1

(i) Nitrogenase 

(ii) Leghaemoglobin : Leghaemoglobin is pinkish pigment found around bacteroides of Rhizobium inside the cells of legume roots that protects the nitrogenase from oxygen. Leghaemoglobin absorbs oxygen and thus it creates anaerobic conditions inside the root nodule. The enzyme nitrogenase is functional only under anaerobic conditions. 

(iii) Ammonium ion is converted into amino acids by two methods : Reductive amination and Transamination.