Legume Rhizobium symbiosis Process

 
Establishment of Legume-­Rhizobium symbiosis involves 2 way transfer of information to the legume root and from legume roots to the Rhizobium. 
 
·         Symbiosis begins with the colonization of the rhizosphere of young roots by rhizobium that can infect the particular host.  
 
·         The plants provides a sheathed “infection thread” which penetrates to the inner cortex and stimulate cortical cells to divide and produce the nodule structure.   
 
·         The developing nodule differentiates vascular tissues which flow of water, nutrients ions. The sugar to supply energy and nitrogen containing products likes amides.  
 
·         ·Since  Nitrogenase  enzyme  required  for  N2    fixation  is  O2  sensitive,  it  is  controlled  by  legume  heamoglobin  in the nodule tissue. The heamoglobin makes healthy legume nodule pink coloured.  Generally, nodule form within 3 weeks after emergence of seedling.
 
In brief, the rhizobium inside the nodule fix significant amount of atmospheric N2 which is used by the legumes in return. The rhizobium gets shelter by receiving other nutrients from the legumes. 
 
Therefore, this is a symbiotic association where both the partners mutually benefited.
 

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