(A) Schematic model for nitrogen remobilization, (B) model of spikelet, (C) cross-section of the dorsal region of grain, and (D) cross-section of large vascular bundle of leaf blade of rice plants. GS1;1 protein was detected in companion cells, phloem-parenchyma cells, and xylem-parenchyma cells in senescing leaf blades (Sakurai et al., 1996), whereas NADH-GOGAT1 protein was located in xylem-parenchyma cells, phloem-parenchyma cells, and mestome sheath cells in developing leaf blade and developing vascular bundle, nucellar projection, nucellar epidermis, and aleurone layer in young grain (Hayakawa et al., 1994), respectively. White arrows in (B) indicate the direction of solute flux from developing vascular bundle to endosperm. Abbreviations: al, aleurone layer; cc, companion cells; dvb, developing vascular bundle; em, embryo; en, endosperm; mc, mesophyll cells; ms, mestome sheath cells; ne, nucellar epidermis; np, nucellar projection; pe, pericarp; ps, parenchyma sheath cell; pp, phloem-parenchyma cell; se, sieve element; xp, xylem-parenchyma cell; xv, xylem vessel element.