Microbiology Procedure
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Index >> Growth of Microorganism >>Root Nodule Bacteria and Legumes

Root Nodule Bacteria and Legumes

Root Nodule Bacteria and Legumes - It is known since long time that fertility of agricultural land can be maintained by crop rotation. Cultivation of leguminous plant could restore the declining levels of land productivity due to cultivation of single crop (say a cereal) for several years.

Root nodules contain large number of bacteroids small, rod shaped or branched bodies (T, V or V-shaped) similar in size and shape to bacteria. M. W. Beijerinck isolated and cultivated the bacteria in 1888.
The bacteria are Gram negative motile rods that are classified in the genus Rhizobium. Their numbers are very variable, depending upon the nature of the soil and on its previous agricultural treatment.

The soil under nonleguminous crop such as wheat may have fewer than 10 Rhizobium cells per gram, the same soil will contain between 10 and 107 cells of Rhizobium following the cultivation of legume crop.

The ability of legume plants to stimulate the growth of Rhizobium in the soil, extends as far as 10 to 20 mm from the roots.

The effect is highly specific. The nature of substance responsible for the stimulation is not yet very well known. The infection of root by Rhizobium resembles that by pathogens.
Nevertheless, this association is not usually considered as parasitism. The plant gains much more from the association. This is thus taken as mutualism.

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