Question: How does Azospirillum bacteria contribute to plant growth?
Options:
Nitrogen fixation
Organic matter recycling
Soil structure
Bulk density
🔑Key Points:
-Nitrogen Fixation – Conversion of atmospheric nitrogen into nitrates so that it can be utilized by plants is termed nitrogen fixation.
-The ability of nitrogen fixation is possessed only by certain prokaryotes containing an enzyme complex called dinitrogenase that catalyzes the reduction of dinitrogen to ammonia. eg: Rhizobium, Azotobacter, Clostridium, Beijerinckia, etc.
-The prokaryotes either fix nitrogen symbiotically (by living in association with the cells of higher plants) or non-symbiotically (by living freely in the soil).
Azotobacter
-It is a non-symbiotic nitrogen-fixing bacteria.
-These are gram-negative, aerobic, free-living that play an important role in the nitrogen cycle
-The first representative of the genus, Azotobacter chroococcum, was discovered and described in 1901 by Dutch microbiologist and botanist Martinus Beijerinck.
🛑 Additional Information::
Rhizobium
-It is the symbiotic nitrogen-fixing bacteria.Â
-Rhizobium is found in the nodules of legumes and is responsible for nitrogen fixation. This was discovered in 1886 by the German physiologists Heleriegal and Wilfarth. Â
Frankia
-It is very similar to Rhizobium Bacteria. It helps in initiating the formation of root nodules. It has a symbiotic relationship with many plants.
-Frankia alni lives in symbiosis with actinorhizal plants in the genus Alnus.
Azospirillum
-It is an aerobic-associated symbiotic nitrogen-fixing organism, it associates with the roots of the grasses and forms a symbiotic relationship.