Biochemical and Biological effects of Kaurene oxidase inhibitor such as Paclobutrazol on vegetative in Mango Cvs. Dashehri, Langra, Chausa and Fazri

Abstract

The compound Paclobutrazol [(2RS, 3RS)-1-(4-chlorophenyl)-4, 4-dimethyle-2- (1, 2, 4 Triazol-1-y)] pentan-3-ethanol was the action of this retardants can be antagonized by Gibberellins (GA3) and ent-Kaurenoic acid. 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, and 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. It is suggested that its main biochemical action is to block the reactions that lead from ent-Kaurene to ent-Kaurenoic acid in the course of Gibberellins biosynthesis courses, reduced vegetative growth more intensively than root growth by this compound.