wht r nodules? explain it's formation n give a diagram 4 it.....

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.

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