Trace the events starting from the coming in contact of Rhizobium to a leguminous root till nodule formation. Add a note on importance of leg haemoglobin.

The reaction carried out by ${\mathrm{N}}_2$ fixing microbes include

(i) $2N{H}_3+3O_2\to +2N{O}_2^{-}+2H^{+}+2H_{2}O$

(ii) $2N{O}_2^{-}+O_2\to 2N{O}_3^{-}$

Which of the following statements about these equations is not true?

Match the element with its associated functions/roles and choose the correct option among given below.