Plant Growth Regulator Reduction of Bypass Shoot Development in Azalea

Abstract

Abstract Foliar spray applications to ‘Gloria’ azalea (Rhododendron obtusum) of daminozide, chlormequat chloride, daminozide/chlormequat chloride combination, ancymidol, paclobutrazol, fluometralin, NAA, and IBA were applied prior to bypass shoot development. All treatments except IBA reduced bypass shoot length. NAA treatments were phytotoxic, and fluometralin inhibited flowering. Rate of flower development was retarded by daminozide, chlormequat chloride, and daminozide/chlormequat chloride combination, but was unaffected by ancymidol, paclobutrazol, fluometralin, NAA, and IBA. Paclobutrazol was the most efficient and effective treatment in reducing bypass shoot length without affecting flower size or time to flower. Chemical names used: butanedioic acid mono (2,2-dimethylhydrazide) (daminozide); 2-chloro-N,N,N-trimethyl-ethanaminium chloride (chlormequat chloride): α-cyclopropyl-α-(4-methoxyphenyI)-5-pyrimidinemethanol (ancymidol): β,[(4-chlorophenyl)methyl)-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol): 2-chloro-N-[2,6-dinitro-4-trifluoromethyl)phenyl]-N-ethyl-6-fluorobenzenemethanamine (fluometralin): 1-naphthaleneacetic acid (NAA): 1H-indole-3-butyric acid (IBA).