Question 8 What are the conditions necessary for fixation of atmospheric nitrogen by Rhizobium. What is their role in N2 -fixation?
Class XI Biology Chapter - Mineral Nutrition Page 205
Answers
Answer:
Following conditions are necessary for fixation of Nitrogen by Rhizobium.
Symbiotic relationship between Rhizobium and roots- necessary for the formation of root nodules.
Necessity of a reducing environment
Nitrogenase enzyme – synthesizes ammonia
ATP- is required for the synthesis of ammonia
NAD(P) H2 or FMNH2 is a source of reducing power
Ferredoxin – acts as an electron donor
Keto acids picks up amino group.
nitrate as a substrate – creates reduced availability of nitrate
Role of Rhizobium in N2 fixation:
They fix atmospheric nitrogen in a form that can be used by plants i.e., ammonia, using the nitrogenase enzyme.
Plant, in turn, deliveries bacteria with proteins, carbohydrates and enough oxygen so that they do not disturb the fixation process.
A plant protein – Leghaemoglobin assists in providing oxygen for respiration process while free oxygen concentration level is still low enough to not hinder the nitrogenase activity.