Question

Which one among the following can fix atmospheric nitrogen? Why?

• Mycorrhiza of Pinus
• The coralloid root of Cycas
  

Answer 1

• Mycorrhizal fungi themselves do not fix nitrogen but bacteria that may associate with them can. Generally, mycorrhiza improves the health of the plant and their roots so diseases may cause less damage.
  
• Within the colloidal root is the cyanobacterial zone, which is the region inhabited by cyanobacteria. All cyanobacteria in symbiosis with cycas have the ability to fix nitrogen.