Ammonium assimilation inhibitors weaken the growth of moso bamboo seedlings through metabolic dysregulation

Background The uncontrolled expansion of moso bamboo ( Phyllostachys edulis ) in subtropical regions threatens forest ecosystem integrity and biodiversity, yet effective control measures are lacking. Because moso bamboo preferentially utilizes ammonium (NH 4 + ) and relies heavily on the glutamine synthetase/glutamate synthase (GS/GOGAT) pathway for its assimilation, we hypothesized that inhibiting this key metabolic route could suppress its growth. Methods An L 9 (3 4 ) orthogonal experimental design was employed to assess the effects of three NH 4 + assimilation inhibitors, phosphinothricin, methionine sulfoximine, and azaserine (AZA), at varying concentrations on the growth and nitrogen metabolism of moso bamboo seedlings. Results Combined inhibitor treatments significantly suppressed seedling growth, reduced fresh weight, and induced profound metabolic dysregulation. This was characterized by markedly decreased activities of GS, GOGAT, and glutamate dehydrogenase (GDH), along with lowered glutamate (Glu) content, concomitant with a substantial accumulation of tissue NH 4 + . Under the present concentration settings, phosphinothricin showed a stronger inhibitory trend, followed by methionine sulfoximine and AZA, and all the effects were dose-dependent. Significant inhibition was observed in both shoots and roots, except that AZA did not significantly affect GDH activity. Critically, fresh weight, Glu content, and the activities of GS, GOGAT, and GDH were all significantly positively correlated, and each was strongly negatively correlated with NH 4 + accumulation. Furthermore, GS and GOGAT demonstrated a tighter functional coupling than they did individually with GDH. Thus, our results indicate a direct mechanistic link between the targeted inhibition of NH 4 + -assimilation enzymes, the consequent disruption of core nitrogen metabolism, and the suppression of bamboo growth. This provides a robust theoretical foundation for developing novel, biochemistry-based strategies to control moso bamboo encroachment.