1.4.1.14 agriculture in Phe-supplied poplars, decreased enzymatic activities of nitrate reductase, glutamate synthase and glutamate dehydrogenase and elevated activities of nitrite reductase, phenylalanine ammonia lyase, glutamine synthetase and asparagine synthase are found in the Phe-treated roots. Accordingly, reduced concentrations of NH4+, NO3- and total N, and enhanced N-use efficiencies are detected in Phe-supplied poplars. The mRNA levels of nitrite reductase, glutamine synthetase 2, NADH-dependent glutamate synthase, glutamate dehydrogenase and asparagine synthetase 2 are downexpressed in Phe-treated roots and/or leaves 763765 1.4.1.14 additional information possible relationship between NADH-GOGAT, IDH and GDH, IDH is a good candidate to generate the 2-oxoglutarate required for NH4+-induced NADH-GOGAT activity in rice roots, GDH shows no significant differences in its localization between the conditions with or without NH4+ application 670544