This invention concerns certain pyridazinylurea compounds and their use as plant regulators.
Plant regulators are hormone-like substances which influence growth and development of plants, as inhibitors or promoters of growth. Sometimes the same compound can both inhibit and promote growth, depending upon the rate of application. Plant regulatory activity is reflected in a variety of ways, including one or more of cell enlargement, leaf and organ abscission, retardation of senescence, release of apical dominance, fruit set and growth, leaf growth, light response, protein synthesis, and other effects. In economic crops and ornamentals, plant regulators have enormous potential as herbicides, rooting promoters, flowering stimulants, fruit developers, and as agents to control or induce seedlessness, plant shape, and the setting, thinning and dropping of fruit. The most familiar classes of plant regulators are the auxins, gibberellins, cytokinins, abscisic acid and ethylene, but the search continues for even more active plant regulating compounds, including compounds having specific forms of regulator activity.
Representative of research efforts in the field are the compounds disclosed in U.S. Pat. Nos. 4,063,928 (substituted pyridinyloxy(thio)phenyl acetamides, ureas and urea derivatives), 4,193,788 (N-(2-chloro-4-pyridyl)ureas and thioureas), 4,308,054 (other pyridyl ureas) and 4,331,807 (N-(4-pyridazinyl)-N'-phenylureas).