Question

Refer the given passage and answer the following questions.

At present the primary nutrient which limits the agricultural yield is nitrogen (N). Some plants are capable to produce more$N_2$ than they consume. These plants show symbioticz relationship with $N_2$-fixing bacteria such as Rhizobium. These bacteria produce root nodules in leguminous plants and convert atmospheric $N_2$ into nitrogenous compounds. Rhizobium bacteria are gram negative bacteria, which show host specificity and fix $N_2$ in the presence of a red pigment called leghaemoglobin. It protects nitrogen fixing enzyme nitrogenase from oxygen.

Which of the following statements is incorrect?

• A. Leghaemoglobin functions as oxygen scavenger during $N_2$ -fixation.
• B. Enzyme nitrogenase, which is required to fix atmospheric $N_2$, is active in the presence as well as absence of oxygen.
• C. N, P and K are referred to as critical elements for crop plants as they easily become deficient in soil due to higher plant requirement and repeated cultivation.
• D. The coordinated activities of the legume and Rhizobium bacteria depend on chemical interactions between the symbiotic partners.

Answer 1

Answer: (B)

Enzyme nitrogenase, which is required to fix atmospheric $N_2$, is active in the presence as well as absence of oxygen.

Nitrogenase is a nitrogen fixing enzyme produced by nitrogen fixing bacteria. It is inactive in the presence of oxygen. Leghaemoglobin produced by the host cells acts as an oxygen scavenger and protects nitrogenase from oxygen.