Roots of legumes have the ability to form a symbiotic relationship with nitrogen-fixing rhizobial bacteria to form nodules, highly specialized organs in which atmospheric dinitrogen is reduced to ammonia. Two types of legume nodules have been defined: determined and indeterminate nodules (Hadri and Bisseling, 1998). Differences between determined and indeterminate nodules could occur because of different vascular bundle arrangements and other anatomical features (Brown and Walsh, 1994).