influcnce of naphthalic anhydride and I-Aminobenzotriazole on maize resistance to herbicides-interferences with growth

A lachlor, metolachlor and particularly atrazine significantly decreased fresh and dry weights of maize shoots. The magnitude of reduction being greater during the first 5 days; a partial recovery was set in thereafter. Naphthalic anhydride [NA] relieved these effects while 1-aminobenzotriazole [ABT] showed cumulative reductions Meantime, the three herbicides under investigation increased abscisic acid [ABA] significantly. These increases seemed to be partially nullified by NA but being unaffected by ABT. On the other hand, all herbicides provoked significant decreases in indole acetic acid [IAA] content, the alachlor effect was relatively small. An immediate recovery in IAA content was induced by NA whilst ABT appeared to augment IAA inhibition. Meanwhile the activities of IAA- oxidase and peroxidase were significantly increased by herbicides. The enzyme activities did not after by NA longer but being further propagated by ABT. The recovery of IAA by NA was confirmed by lesser enzyme activities, may be due to the detoxification of these herbicides to non-toxic compounds. Moreover the increases in enzyme activities could explain the IAA reduction by herbicides, particularly when ABT was present, probably because of the retardation in herbicide breakdown and consequently increase the Phytotoxicity. The conflicting changes in ABA and IAA contents as well as in enzyme activities could explicate the differential growth responses to different treatments

influcnce of naphthalic anhydride and I-Aminobenzotriazole on maize resistance to herbicides-Secondary metabolism responses

Dry weight of maize shoots was significantly decreased following treatments with alachlor, metolachlor and atrazine; more reduction was observed with atrazine. The presence of naphthalic anhydride [NA] relieved these reductions whilst I-aminobenzotriazole [ABT] showed cumulative effects. Meanwhile activities of phenylalanine ammonia lyase [PAL,], tyrosine ammonia lyase [TAL] and chalcone isomerase [CI] were significantly increased; alachlor seemed the most inductive. The presence of NA counterbalanced the enhanced activities whereas ABT showed much reduction. Phenolic compounds and anthocyanin significantly increased by alachlor and metolachlor while atrazine had no effect. These increased levels became comparable to that of controls by NA but significantly diminished by ABT. The responses of PAL, TAL, and Cl preceded that of phenolics and anthocyanin confirming the controlling role of these enzymes. Moreover, these findings reveal the occurrence of an induced stress status. The counterbalancing action of NA on herbicide effects indicates the retraction of these conditions, might be due to herbicide detoxification. In contradistinction, ABT reduced these levels suggesting more decreases in enzyme concentrations probably because of the sinking of herbicide degradation through the inhibition or P450s. So a protraction of herbicide persistence, and consequently increased the phytotoxicity, could occur within the plant