Defoliation eliminates photosynthesis and reduces dinitrogen fixation of alfalfa (Medicago sativa L.) forcing plants to rely on taproot C and N reserves for herbage regrowth and survival. Our objective was to determine the impact of taproot N pools on growth of alfalfa germplasms differing in nodule effectiveness. ‘Saranac' alfalfa and an ineffective nodulating (IN) germplasm derived from Saranac were seeded in pots, inoculated with Rhizobium melitoti, and provided complete Hoagland's nutrient every five days in order to facilitate establishment. After 129 days the complete Hoagland's solution was replaced with minus-N Hoagland's solution for one regrowth cycle in order to deplete soil N levels and internal N pools, especially those in IN Saranac plants. Plants were defoliated and after Day 10 of regrowth, one-half the pots were again provided complete Hoagland's nutrient solution to raise N pool levels in one-half of the IN Saranac plants, while the other half were maintained on -N Hoagland's solution for three weeks. Plants were sampled five times during the three weeks of contrasting N nutrition. Plants were defoliated on Day 35 of this regrowth cycle and roots and crowns were transplanted into coarse river sand. All plants were provided minus-N Hoagland's for the remainder of the study and sampled weekly. Herbage growth and taproot N pools of Saranac were not influenced by N fertilization. At transplanting taproots of IN Saranac plants provided N had higher protein concentrations and the 15, 19 and 32 kD vegetative storage proteins (VSPs) were present. IN+N Saranac plants had greater herbage regrowth when compared to IN-N Saranac plants. In contrast, concentrations of starch and sugars were generally lower in taproots of IN Saranac plants provided N when compared to their minus-N counterparts. Taproot N pools, and abundance of taproot VSPs were positively associated with herbage regrowth of N-stressed alfalfa plants.