Inhibition of nitrate and nitrite reductase induction in wheat by sandoz 9785

Abstract

The effect of a non-bleaching pyridazinone herbicide [4-chloro-5(dimethylamino)-2-phenyl-3(2H) pyridazinone; SANDOZ 9785; BASF 13-338] on the induction of nitrate reductase (NR) and nitrite reductase (NIR) has been studied in leaf segments and seedlings of wheat. The induction of both NR and NIR was inhibited, albeit differentially, in detached green leaves as well as intact green seedlings grown in the presence of SAN 9785 and nitrate. The inhibition of NR and NIR induction due to SAN 9785 treatment occurred in the absence of photobleaching (detached leaves) or in the presence of marginal photobleaching (intact seedlings). Seedlings grown in the presence of SAN 9785 without nitrate showed a reduced capacity for induction of NR and NIR. The NADH-DCPIP reductase activity was not inhibited in SAN 9785-grown seedlings. The cause for inhibition of NR activity was neither inactivation of NR in vivo or in vitro, nor a reduction in the level of soluble protein. Both DCMU and SAN 9785 inhibited 14CO 2 fixation and induction of NR and NIR under similar conditions of treatment.