Case Study/Passage Based Questions:
Question 1:
At present the primary nutrient which limits the agricultural yield is nitrogen (N). Some plants are capable to produce more N2 than they consume. These plants show symbiotic relationship with N2-fixing bacteria such as Rhizobium.
These bacteria produce root nodules in leguminous plants and convert atmospheric N2 into nitrogenous compounds. Rhizobium bacteria are gram negative bacteria, which show host specificity and fix N2 in the presence of a red pigment called leghaemoglobin. It protects nitrogen fixing enzyme nitrogenase from oxygen.
(i) Which of the following statements is incorrect?
(A) Leghaemoglobin functions as oxygen scavenger during N2-fixation.
(B) Enzyme nitrogenase, which is required to fix atmospheric N2 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.
Show Answer
Answer: B(ii) Read the given statements and select the correct answer.
Statement 1: Rhizobium bacteria can also live freely in the soil and cany out N2-fixation by themselves.
Statement 2: Such Rhizobium bacteria are called free-living N1-fixing bacteria.
(A) Both statements 1 & 2 are true and statement 2 is the correct explanation of statement 1.
(B) Both statements 1 & 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.
