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 a symbiotic 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.

Read the given statements and select the correct answer.

Statement 1: Rhizobium bacteria can also live freely in the soil and carry out $N_2$-fixation by themselves.
Statement 2: Such Rhizobium bacteria are called free-living $N_2$-fixing bacteria.

• A. Both statements 1 and 2 are true and statement 2 is the correct explanation of statement 1.
• B. Both statements 1 and 2 are true but statement 2 is not the correct explanation of statement 1
• C. Statement 1 is true and statement 2 is false.
• D. Both statements 1 and 2 are false.

Answer 1

Answer: (D)

Both statements 1 and 2 are false.

Rhizobium is a symbiotic bacterium which forms association with nodulated roots of different legumes. The bacterium obtains shelter and food from legume and in turn it performs nitrogen fixation inside nodules. Rhizobium lives in mutually beneficial association with other organisms and hence is known as symbiotic bacterium.

So, the correct answer is 'Both statements 1 and 2 are false.'