Rice plants develop the fibrous root system which consists of several sets of numerous primary roots initiating from each stem node. There is a definite correlation between leaves and roots in their emergence and development; when the (n) th leaf of a stem is developing, a set of primary roots emerges from the (n-3) th node of the same stem. By using this rooting habit, relations between the growth of roots initiating from the different nodes were investigated with special reference to the nitrogcn movement from shoots to roots. Roots developing during the period of the 9th leaf development were designated as the roots from the 6th node (6th nodal roots) and they were separated from those emerging from the other nodes by tying up into a loose bundle with a fine string of nylon just before the emergence of the 10th leaf. Similarlyr, the roots emerging during the development of the 8th and 10th leaves were separated and designated as the 5th and 7th nodal roots, respectively. For more than 2 weeks prior to the start of experiment, plants were kept in the Kasugai's culture solution containing ¹⁵NH₄⁺ as a tracer. At the beginning of growth of the 6th nodal roots (Day 0 of experiment), plants were transplanted into a culture solution without tracer (CS-plant) or into tap water (W-plant), and the process of growth of the 5th, 6th, and 7th nodal roots was examined for 15 days thereafter. The number of the 6th nodal roots increased 2ts the 9th leaf blade elongated and expanded, then reached maximum at Day 7 when the 7th nodal roots began to emerge. Total length of the 6th nodal roots increased throughout the experimental period. The root length of W-plant exceeded that of CS-plant. The maximum increasing rates of number and of total length of the 6th nodal roots were found during the period from Day 2 to Day 4 and from Day 4 to Day 9, respectively. In a set of the 6th nodal roots, the variation range of root length expanded markedly during the period from Day 4 to Day 7, and the percentage of the primary roots having branches also increased eminently. Dry weight of the 6th nodal roots increased progressively during experimental period in both CS- and W-plant. On the other hand, total nitrogen and ¹⁵N content of the 6th nodal roots increased up to Day 9, then decreased. Absorption of nitrogen from nutrient solution continued for the first 7 days of the experimental period, therefore, the total amount of nitrogen fixed in the CS-plant increased during this period, while the amount was kept constant throughout the experimental period in W-plant. In both CS- and W-plant, however, total nitrogen and ¹⁵N content of the 5th nodal roots ceased to increase on Day 4 when those in the 6th nodal roots began to increase. Similar relation between 6th and 7th nodal roots was found on Day 9 in CS-plant and on Day 11 in W-plant. From these results it is likely to be considered that nitrogen supply from shoot to growing roots terminated at the onset of development of the new set of roots emerging from the nearest upper node. It is conceivable that the growth of nodal roots largely depends upon the nitrogen supplied from shoot rather than upon the nitrogen absorbed from culture solution.