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Question
In which of the following family, bacteria fix nitrogen in soil by symbiosis?
In which of the following family, bacteria fix nitrogen in soil by symbiosis?
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Solution
The correct option is A Leguminosae
The history of legumes is tied in closely with that of human civilization, appearing early in Asia, the America and Europe by 6,000 BCE, where they became a staple, essential as a source of protein. Their ability to fix atmospheric nitrogen reduces fertilizer costs for farmers and gardeners who grow legumes, and means that legumes can be used in a crop rotation to replenish soil that has been depleted of nitrogen. Legume seeds and foliage have a comparatively higher protein content than non-legume materials, due to the additional nitrogen that legumes receive through the process. Some legume species perform hydraulic lift, which makes them ideal for intercropping. Of the 10 families within the Rosidae, 8 have nodules formed by actinomyces (Betulaceae, Casuarinaceae, Coriariaceae, Datiscaceae, Elaeagnaceae, Myricaceae, Rhamnaceae and Rosaceae) and the two remaining families, Ulmaceae and Fabaceae have nodules formed by rhizobia bacteria. The rhizobia and their hosts must be able to recognize each other for nodule formation to commence. Rhizobia are specific to particular host species although a rhizobia species may often infect more than one host species. This means that one plant species may be infected by more than one species of bacteria. Thus, option A is correct. In Solanaceae, Malvaceae and Cruciferae, bacteria does not fix nitrogen in soil by symbiosis. Thus, other options are wrong.
The history of legumes is tied in closely with that of human civilization, appearing early in Asia, the America and Europe by 6,000 BCE, where they became a staple, essential as a source of protein. Their ability to fix atmospheric nitrogen reduces fertilizer costs for farmers and gardeners who grow legumes, and means that legumes can be used in a crop rotation to replenish soil that has been depleted of nitrogen. Legume seeds and foliage have a comparatively higher protein content than non-legume materials, due to the additional nitrogen that legumes receive through the process. Some legume species perform hydraulic lift, which makes them ideal for intercropping. Of the 10 families within the Rosidae, 8 have nodules formed by actinomyces (Betulaceae, Casuarinaceae, Coriariaceae, Datiscaceae, Elaeagnaceae, Myricaceae, Rhamnaceae and Rosaceae) and the two remaining families, Ulmaceae and Fabaceae have nodules formed by rhizobia bacteria. The rhizobia and their hosts must be able to recognize each other for nodule formation to commence. Rhizobia are specific to particular host species although a rhizobia species may often infect more than one host species. This means that one plant species may be infected by more than one species of bacteria. Thus, option A is correct. In Solanaceae, Malvaceae and Cruciferae, bacteria does not fix nitrogen in soil by symbiosis. Thus, other options are wrong.
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