To evaluate the role of cytokinin in the source-sink relationship, panicles of rice were cut from the stem at the panicle emergence stage. Xylem sap exudates were collected using the stem cut method and the cytokinin concentration in the collected sap was determined by bioassay and further analysis using enzyme-linked immunosorbent assay. The rate of cytokinin translocation from roots to shoots decreased continuously after panicle initiation, whereas, when the panicle was removed, the rate increased by up to 1.5-fold, at which time no cytokinin was found in the plants with particles. Retardation of leaf senescence was not observed and nitrogen concentration in the leaves continued to decrease after panicle removal, irrespective of cytokinin (mainly dihydrozeatin riboside and trans-zeatin riboside) level. Thus, leaf autonomy is regulated by an endogenous program of nitrogen translocation from the leaf regardless of cytokinin level in the xylem.