root primordium root nodule primordium 2013-11-07T08:56:21Z BTO:0005444 BrendaTissueOBO Marion To form a root nodule primordium, fully differentiated root cortical cells have to be developmentally reprogrammed, which starts with mitotic activation of these cells. This is induced by Nod factors and leads to the formation of nodule primordia. Upon infection by rhizobia these primordia subsequently differentiate in nodules.