AP BIOLOGY

Detailed explanation-1: -Bacteria in the soil or in plant roots convert nitrogen gas from the environment into solid nitrogen molecules that plants can utilize in the soil. The bacteria within the nodules convert free nitrogen to nitrates, which the host plant uses for growth.

Detailed explanation-2: -Nitrogen-fixing bacteria in the soil and within the root nodules of some plants convert nitrogen gas in the atmosphere to ammonia. Nitrifying bacteria convert ammonia to nitrites or nitrates. Ammonia, nitrites, and nitrates are all fixed nitrogen and can be absorbed by plants.

Detailed explanation-3: -Nitrogen-fixing bacteria fix atmospheric nitrogen to ammonia and then convert it into nitrites and nitrates which can then be taken up by plants. This process is called biological nitrogen fixation. Nitrogen-fixing bacteria may be free-living or symbiotic.

Detailed explanation-4: -Rhizobium is the type of bacteria which is found in the roots of leguminous plants and converts atmospheric nitrogen into nitrates.

Detailed explanation-5: -The symbiotic nitrogen-fixing bacteria invade the root hairs of host plants, where they multiply and stimulate formation of root nodules, enlargements of plant cells and bacteria in intimate association. Within the nodules the bacteria convert free nitrogen to ammonia, which the host plant utilizes for its development.