COMPARATIVE EFFECTS OF ALACHLOR, METOLACHLOR, ATRAZINE, FLUOMETURON AND TRIFLURALIN ON THE ENDOGENOUS PHYTOHORMONES IN MAIZE AND SOYBEAN

The effects of Alaclor, Metolachlor, Atrazine, Fluometuron and Triflur alin on the levels of the endogenous phytohormones in maize and soybea n seedlings were investigated. All the employed herbicides, at the rec ommended field rates, resulted in remarkable increases in ABA content of maize and soybean tissues during the early stages of treatment (up to day 8) except in the case of maize roots where a marked inhibition of ABA formation was observed following treatment with alachlor and me tolachlor. Nevertheless, both plants were able to bring about a comple te recovery from alachlor and metolachlor actions 12 days after treatm ent; meanwhile the stimulatory effects of fluometuron, trifluralin and atrazine upon ABA production continued up to the last interval (day 1 2). Moreover, fluometuron and trifluralin attenuated the production of IAA and GA3 in both maize and soybean tissues, and zeatin, in maize t issues, to a much greater extent than did atrazine, alachlor or metola chlor. These observations clearly indicate the fact that both maize an d soybean seedlings have greater resistance or detoxifying ability tow ards alachlor, metolachlor and atrazine than towards trifluralin or fl uometuron.