ROUTE OF NITRATE-NITROGEN ASSIMILATION IN THE ROOT OF DATURA-STRAMONIUM L

Datura roots were pressure-infiltrated with 400 μg ml-1 15N-nitrate feeding solutions with and without the addition of 7 mM L-methionine-DL-sulphoximine (MSO), a glutamine synthetase inhibitor. Over a 30 min time course the main diversion of newly reduced 15N in MSO untreated roots was to glutamine. In MSO-treated roots ammonia assimilation into amino compounds was completely suppressed, with resultant accumulation of a large 15N ammonia pool. This treatment also caused marked concentrational changes in the free amino compound pools, suggesting that conditions of nitrogen stress had been induced. Glutamate dehydrogenase activity was unaffected by the MSO treatment.The results are consistent with the concept that the glutamine synthetase/glutamate synthase pathway is the major route of newly reduced nitrogen assimilation in Datura roots. © 1979 Oxford University Press.