Volume 4, Issue 3 (March 2007)
Development of Fast Dissolving Concentrated Gibberellin Water Soluble Granular Formulations
Gibberellins, a major group of naturally occurring plant hormones, are diterpenoid acids, known to influence a range of plant developmental processes including stem elongation, germination, dormancy, flowering, sex expression, enzyme induction, fruit size and quality, and leaf and fruit senescence. Gibberellins are commercially produced by fermentation of natural fungus, Gibberella fujikuroi. The most commonly used Gibberellic acid, GA3, is primarily formulated as solutions (2 to 5 % in isopropyl alcohol, 10 % in methyl alcohol), as 5 to 20 % wettable or soluble powders, or both, as 3.1 % soluble granules or as 1 to 10-g effervescent tablets. The other frequently used gibberellins, GA4+7, are primarily formulated as 1 to 4 % solutions either in tetrahydrofurfuryl alcohol (THFA) or in propylene glycol. Of the solvents currently used, isopropyl alcohol and methyl alcohol offer severe disadvantages such as flammability, toxicity, and restrictions in manufacturing, packaging, labeling, transportation, and warehousing. The THFA used in some of the formulations is considered corrosive to the eye and skin. Low solubility of gibberellins in propylene glycol does not permit solution formulations with greater than 2 % wt/wt gibberellins. The powder formulations are not user friendly and require quite a long time to achieve true solubility of the active component in tank mixes. Due to low solubility and undesirable hydrolysis, it has not been possible to formulate gibberellins in aqueous systems. This paper will present formulation studies leading to the development of stable, high potency (GA3 at 40 % wt/wt and higher; GA4+7 at 10 % wt/wt and higher), dust free, instantly water wettable, dispersible, and soluble Gibberellin plant growth regulator granular formulations by low pressure extrusion methodology. Field biological efficacy studies on grapes showed concentrated water soluble granular formulation either equivalent or superior to the standard powder formulation.