Question

Which one of the following plants can fix nitrogen from air?
A.Pea
B.Wheat
C.Rice
D.Maize

Answer 1

Hint: The phenomenon of conversion of free nitrogen into nitrogenous salts to make it available for absorption by plants is called nitrogen fixation. Nitrogen fixation is divided into physical nitrogen fixation and biological nitrogen fixation

Complete step by step answer:
-One of the important nitrogen fixing bacteria – Rhizobium fixes nitrogen in symbiotic association with roots of leguminous plants.
Examples are pea , beans, Alfa-Alfa, clover, lupines
-Initially the bacteria grow in the soil near the roots of higher plants where they fail to fix nitrogen.
-These bacteria when come in contact with roots of leguminous plants , interact chemically and enter into roots through root hairs.
-Entry of bacteria into the root hair depend upon various chemical agents
The enzyme from the bacteria degrades the parts of the root hair cell wall which produces thread like structures called infection thread.
-The bacteria multiply and invade the infection thread
-Finally the invading bacteria reaches upto the inner cortex where they enter into cells and stimulate them to divide.
-The proliferating cells form a knob-like protuberance called root nodule.

So the correct answer is option is A. Pea

Note:
-Nitrogen so fixed is converted to nitrates and then to ammonia .
-Biological nitrogen fixation is also called associative symbiotic nitrogen fixation.
-Leguminous plants have a symbiotic association with the nitrogen fixing bacteria.