Involved in glutamate biosynthesis and plays a major role in the primary ammonium ions assimilation in seedling roots. May be involved in the reutilization of glutamine in developing organs. Plays a role in the development of tillers. 2 L-glutamate + NAD(+) = 2-oxoglutarate + H(+) + L-glutamine + NADH Binds 1 [3Fe-4S] cluster. Amino-acid biosynthesis; L-glutamate biosynthesis via GLT pathway; L-glutamate from 2-oxoglutarate and L-glutamine (NAD(+) route): step 1/1. Energy metabolism; nitrogen metabolism. Monomer. Highly expressed in roots. By ammonium supply in roots. Inhibition of the main root elongation when grown in presence of ammonium chloride. Reduced plant height, biomass and panicle number. Belongs to the glutamate synthase family.