We investigated the role of glutamine synthetases (cytosolic GS1 and chlo-roplast GS2) and glutamate synthases (ferredoxin-GOGAT and NADH-GOGAT) in the inorganic nitrogen assimilation and reassimilation into amino acids between bundle sheath cells and mesophyll cells for the remo-bilization of amino acids during the early phase of grain filling inZea mays L.