A series of 1-atyl-l, 4-dihydro-3-acylhydrazinocarbonyl-6-methyl-4- pyridazinones, related to the plant growth regulating effect (GRE), were synthesized and tested in excised Cucumber cotyledon root- formation. The bioassay shows that the tide compounds possess promoting Cucumber cotyledon root-formation activity. And the activity was influenced by the nature of the substituents. The quantitative relationship between the structure of the compounds and their GRE activity was analyzed, using the physicochemical parameters of the substituents and regression analyzed. The result shows that both hydrophobic parameter and electronic parameter of the substituents are the major one in affecting the activity. This offers important structural insights into designing highly active compounds prior to their synthesis.

Key words: HYDRAZIDE P;PYRIDAZINONE P;PLANT GROWTH REGULATORS, STRUCTURE ACTIVITY RELATIONSHIP;BIOLOGICAL ACTIVITY