Question

What does Nessler’s reagent identify? How about Trommsdorf’s and other reagents used? What role do Azotobacter and Rhizobium play in a symbiotic relationship with legumes

Answer 1

Nessler’s reagent (alkaline solution of potassium tetraiodomercurate(II) )is used to test the presence of ammonia in a sample. A yellow color indicates presence of ammonia and thus it was not oxidized to nitrite, while as absence of any colour change indicate absence of ammonia and presence of nitrite.

To detect presence of nitrite, Trommsdorf’s reagent (Zinc iodide-starch solution) is used along with H2SO4. The presence of blue-black coloration indicates presence of nitrite and no change of colour indicate absence of nitrite.

The process of conversion of atmospheric N2 into ammonia and the to protein with the help of microorganisms is called nitrogen fixation . symbiotic bacteria Rhizobium infest root nodules of leguminous plants in presence of Azotobacter to fix atmospheric nitrogen using nitrogenase enzyme. Azotobacter produces extracellular polysaccharide slime layer, which helps to minimize diffusion rate of oxygen to the cell