Paclobutrazol: a novel plant growth regulator and multi-stress ameliorant

Abstract

Paclobutrazol [(2RS, 3RS)-1-(4-chlorophenyl)-4, 4-dimethyl-2-(1H-1, 2, 4-trizol-1-yl)-pentan-3-ol], is one of the members of triazole family having growth regulating property. The growth regulating properties of paclobutrazol are mediated by changes in the levels of important plant hormones including the gibberellins (GAs), abscisic acid (ABA) and cytokinins (CK). Paclobutrazol (PBZ) affects the isoprenoid pathway, and alters the levels of plant hormones by inhibiting gibberellin synthesis and increasing cytokinins level. When gibberellins synthesis is inhibited, more precursors in the terpenoid pathway accumulate and that resulted to the production of abscisic acid. PBZ has been used to provide plant protection against numerous abiotic stresses such as chilling, water deficit stress, flooding and salinity. Paclobutrazol acts as stress protectant by maintaining relative water content, membrane stability index, photosynthetic activity, photosynthetic pigments and protects the photosynthetic machinery by enhancing the level of osmolytes, antioxidant activities and level of endogenous hormones and thereby enhances the yield.