Mineral Nutrition Question 48

48. A free living nitrogen-fixing cyanobacterium which can also form symbiotic association with the water fern Azolla is

[2004]

(a) Tolypothrix

(b) Chlorella

(c) Nostoc

(d) Anabaena

Show Answer

Answer : d

Hints & Solution

(d) The freshwater fern Azolla harbours Anabaena (a blue green alga) in its leaf cavities. Chlorella is simply a green alga. Nostoc is a free living cyanobacteria involved in $N_2$ fixation and so is Tolypothrix.