Paclobutrazol is the ISO common name for an organic compound that is used as a plant growth retardant and triazole fungicide. Chemically it is 1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pentan-3-ol (IUPAC name), CAS 76738-62-0, molecular formula C15H20ClN3O and molar mass about 293.8 g mol^-1. It is a white to off white crystalline solid with low water solubility and good solubility in common organic solvents such as methanol and acetone. Paclobutrazol acts primarily by interfering with gibberellin biosynthesis through inhibition of specific cytochrome P450 dependent steps, producing reduced internode elongation, more compact canopy architecture and altered flowering behaviour in treated plants. Applications include foliar sprays, soil drenches and localized trunk or root treatments in horticultural and agricultural practice; efficacy, dose and legal status vary by crop and jurisdiction.
Technical paclobutrazol specifications typically target a high assay and tight impurity limits; a common technical grade specification is assay by HPLC at not less than 97.0 to 98.0 percent w/w. Typical limits for related substances are commonly set at not more than 0.5 percent w/w for any single related compound and not more than 1.0 percent w/w total related compounds and unspecified impurities. Typical impurity categories comprise triazole-related byproducts, chlorophenyl-containing analogs, oxidation products (dehydrogenated or ketone derivatives), stereoisomeric mixtures and low-level dechlorinated species. Residual solvent limits are usually below 0.2 percent w/w and heavy metals and chlorinated solvent residues are controlled to pharmacopeial or regulatory thresholds. Exact impurity profiles and numerical limits should be taken from the supplier certificate of analysis or the product specification sheet for regulatory compliance.
Paclobutrazol is used as a plant growth regulator to reduce vegetative shoot extension, produce more compact plants, and in some cases to improve flowering and fruit set; it is applied as foliar sprays, soil drenches or localized treatments. It is also classified within triazole chemistry and may exhibit fungicidal activity, but its primary commercial role is as a growth retardant. Use, recommended rates and permitted crops are subject to local label approvals and regulations.
Paclobutrazol has been used by some growers in durian production to manage canopy size and influence flowering, but its use depends on local registration, recommended practices and safety rules. Because regulatory approvals, application methods and withdrawal periods differ by country and product formulation, growers should follow local extension guidance and labeled instructions before using paclobutrazol on durian.
Paclobutrazol has the IUPAC name 1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pentan-3-ol, molecular formula C15H20ClN3O, CAS number 76738-62-0 and a molar mass of about 293.8 g mol^-1. It contains a 4-chlorophenyl ring, a tertiary alcohol-bearing pentane chain with two methyl groups at C4 and a 1,2,4-triazole ring connected at C2; the molecule contains stereocenters and may be sold as a racemate or defined stereoisomer mix depending on the manufacturer.
No, paclobutrazol is not a plant growth hormone. It is a growth regulator that inhibits biosynthesis of endogenous gibberellins, the plant hormones responsible for stem elongation. By reducing gibberellin production, paclobutrazol reduces elongation growth and modifies plant form, but it does not function as a hormone itself.
