curling of root hair tips during nitrogen fixation is caused due to nod factor.

bt is this nod factor produced by bacteria and thenninduced into the root or is it produced by the plant?

also give some info bout nif and fix gene.. n who produces it.

and there s another question ...the corrct ans given is C ..i agree bt cant it be B too?

plz explain ur ans Q- during root nodule formation in legumes

a) nod factors are produced by legumes only

b) nod, nif, fix genes of legumes are activated

c) cytokinin lvl increases in roots.

th c

When the tip of root hairs of leguminous plants comes in contact with the bacteria Rhizobium, it curls and becomes deformed. Bacteria enter inside the curling and invade the root tissue. Sometimes bacteria grow inside the curling and form a membrane bound globular structure. The plant also passes an infection thread of plasma membrane into the curling which starts cell division there. Finally a nodule is formed which separates the infected plant from the others.

These root nodules contain pigments called leghaemoglobin which can combine with oxygen and protect the enzyme nitrogenase. Nitrogenase helps to break down nitrogen molecules for nitrogen fixation.

In leguminous plants, cytokinin inhibits the lateral root formation which helps in curling of root tips during nodule formation. For this reason during nodule initiation, cytokinin level increases in roots.  

The option (b) is not correct as the genes nod(nodule formation), nif (nitrogen fixation) and fix (symbiotic nitrogen fixation) are present inside the chromosomes of bacteria but not in the legumes.