All of the following statements concerning the actinomycetous filamentous soil bacterium Frankia are correct except that Frankia
- can induce root nodules on many plant species
- can fix nitrogen in the free-living state
- forms specialized vesicles in which the nitrogenase is protected from oxygen by a chemical barrier involving triterpene hopanoids
- like Rhizobium, it usually infects its host plant through root hair deformation and stimulates cell proliferation in the host's cortex.
Answer
(2) can fix nitrogen in the free-living state
Solution
As per NCERT, Frankia is a nitrogen-fixing microbe that produces nitrogen-fixing nodules on the roots of non-leguminous plants such as Alnus.
(1) Correct: it induces root nodules on many non-leguminous (actinorhizal) plant species.
(3) Correct: nitrogen fixation takes place in special vesicles whose hopanoid-lipid envelope keeps oxygen away from nitrogenase.
(4) Correct: like Rhizobium, it commonly enters through deformed root hairs and makes cortical cells proliferate to form the nodule.
(2) Incorrect: Frankia is known as a symbiotic nitrogen fixer; its nitrogen fixation is associated with the nodules of its host plant, not with a free-living state.
∴ The exception is statement (2).
Answer: (2)