AP BIOLOGY

Detailed explanation-1: -Symbiotic relationship. Rhizobia are unique in that they are the only nitrogen-fixing bacteria living in a symbiotic relationship with legumes. Common crop and forage legumes are peas, beans, clover, and soy.

Detailed explanation-2: -Legumes are able to form a symbiotic relationship with nitrogen-fixing soil bacteria called rhizobia. The result of this symbiosis is to form nodules on the plant root, within which the bacteria can convert atmospheric nitrogen into ammonia that can be used by the plant.

Detailed explanation-3: -The rhizobia are soil microorganisms that can interact with leguminous plants to form root nodules within which conditions are favourable for bacterial nitrogen fixation. Legumes allow the development of very large rhizobial populations in the vicinity of their roots.

Detailed explanation-4: -The relationship between a host legume and the rhizobia is symbiotic, providing benefits to both participants. Once the rhizobia have established themselves in the root nodule, the plant provides carbohydrates in the form of malate and succinate, and the rhizobia provide ammonia for the formation of amino acids.

Detailed explanation-5: -Nitrogen fixing symbiosis has evolved in several lineages, but not all legumes form symbiosis. Hitherto 12, 000 nodulated legume species are known and each has its own Rhizobium partner(s).