Paclobutrazol as a plant growth regulator

Abstract

Plant growth regulators are chemical substances which govern all the factors of development and growth within plants. The application of plant growth regulators to crops modifies hormonal balance and growth leading to increased yield, enhanced crop tolerance against abiotic stress and improved physiological trait of crops. Paclobutrazol (PBZ) [(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 PBZ are mediated by changes in the levels of important plant hormones including the gibberellins (GAs), abscisic acid (ABA) and cytokinins (CK). PBZ affects the isoprenoid pathway, and alters the levels of plant hormones by inhibiting gibberellin synthesis and increasing cytokinins level and consequent reduction in stem elongation. When gibberellins synthesis is inhibited, more precursors in the terpenoid pathway accumulate and that resulted in the production of abscisic acid. PBZ is more effective when applied to the growing media and application on the growing medium would give longer absorption time and more absorption of active ingredient than foliar spray. The application of PBZ to crops is important in reducing plant height to prevent lodging and in increasing number and weight of fruits per tree, in improving the fruit quality in terms of increases in carbohydrates, TSS, TSS/TA and decreases acidity. It further reduces evapo-transpiration and decreases plant moisture stress by enhancing the relative water content of leaf area and develops resistance in the plants against biotic and abiotic stresses. In addition, it acts as highly active systemic fungicide and used against several economically important fungal diseases. In this review, the current knowledge and possible applications of PBZ, which can be used to improve the growth, yield and quality of crops, have been reviewed and discussed. The role of PBZ to mitigate the harmful effects of environmental stresses in crops is also examined. Moreover, various biochemical and physiological processes leading to improved crop production under the effect of PBZ are discoursed in detail.

Understanding the Role of Gibberellic Acid and Paclobutrazol in Terminal Heat Stress Tolerance in Wheat

“…The triazole-mediated stress protection is due to changes in hormones such as an increase in cytokinins, a transient rise in ABA, and a decrease in ethylene (Soumya et al, 2017 ). It helps in plant stress adoption by maintaining relative water content and electrolyte leakage, and protecting the photosynthetic machinery by enhancing the levels of osmolytes, antioxidant activities, and endogenous hormones; thereby enhancing photosynthetic activity contributing to plant growth and yield (Pinhero and Fletcher, 1994 ; Desta and Amare, 2021 ). Here, we present a comparative study to understand the mechanism of PBZ- and GA 3 -mediated stress tolerance in wheat.…”

Paclobutrazol Improves the Quality of Tomato Seedlings to Be Resistant to Alternaria solani Blight Disease: Biochemical and Histological Perspectives

“…This study produced results that corroborate the findings of a great deal of previous work in promoting growth of plants under stress by applying PBZ. PBZ improves plant tolerance against different stresses by increasing proline content and enzymatic antioxidants [ 14 ], increases fruit yield (due to the relatively stouter canopy of PBZ-treated plants), improving rooting system (which may increase the uptake of water and nutrients) [ 36 ], regulating photosynthetic capacity and delaying leaf senescence [ 37 ], improving the resistance against many plant pathogens [ 38 ], and acting as a systemic fungicide against several economically fungal diseases [ 39 ]. The mode of action of paclobutrazol may include the inhibition of gibberellic acid synthesis in plants, which reduces gibberellins level, slows cell division and elongation (without causing toxicity to cells), and increases cytokinin content, as well as the root activity and C: N ratio.…”

Flowering Mechanisms and Environmental Stimuli for Flower Transition: Bases for Production Scheduling in Greenhouse Floriculture

“…Daminozide also affects flowering in some woody ornamental plants, such as Rhododendron [ 36 ], and delays inflorescence development in azalea [ 37 ]. Historically, triazoles have produced the best compounds for ensuring suitable growth control in a wide range of crops [ 38 ]. More than the compounds mentioned above, other triazoles are used successfully on flowering crops such as flurprimidol, known for its effect on woody ornamentals, including the acidophilic species Rhododendron catawbiense (Michx.).…”