IDENTIFICATION
Common name: Gibberellic acid
Chemical abstracts name: (1α2β,4aα,4bβ,10β)-2,4a,7–trihydroxyl-1-methyl-8-methylenegibb-3-ene-1,10-dicarboxylic acid 1,4a-lactone
Type: Plant growth regulator
CAS RN: [77-06-5]
M.F.: C19H22O6
Mol Wt: 346.4
PHYSICAL CHEMISTRY
Form (appearance): Crystalline solid.
M.P.: 223-225℃ (decomp.)
Solubility.: In water 5 g/l (room temperature). Soluble in methanol, ethanol, acetone, and aqueous alkalis; slightly soluble in diethyl ether and ethyl acetate. Insoluble in chloroform. Potassium, sodium, and ammonium salts: Readily soluble in water (potassium salt 50 g/l).
Stability: Dry gibberellic acid is stable at room temperature, but slowly undergoes hydrolysis in aqueous or aqueous alcoholic solutions, DT50 (20 gibberellic acid) c. 14 d (pH 3-4), 14 d (pH 7). In alkalis, undergoes a rearrangement to less biologically-active compounds. Decomposed by heat.
Pka: 4.0
APPLICATION
Formulation types: EC; SG; SP; TB; Crystals.
Mode of action: Acts as a plant growth regulator on account of its physiological and morphological effects in extremely Iow concentrations. Translocated. Generally affects only the plant parts above the soil surface.
Uses: Has a variety of applications, e.g. to improve fruit setting of clementines and pears (especially William pears): to loosen and elongate clusters and increase berry size in grapes: to control fiuit maturity by delaying development of the yellow colour in lemons; to reduce rind stain and retard rind ageing in navel oranges: to counteract the effects of cherry yellows virus diseases in sour cherries: to produce uniform seedling growth in rice; to promote elongation of winter celery crop: to induce uniform bolting and increase seed production in lettuce for seed; to break dormancy and stimulate sprouting in seed potatoes; to extend the picking season by hastening maturity in artichokes; to increase the yield in forced rhubarb: to increase the malting quality of barley; to produce brighter-coloured, firmer fruit, and to increase the size of sweet cherries; to increase yields and aid harvesting of hops; to reduce internal browning and increase yields of Italian prunes; to increase fruit set and yields of tangelos and tangerines; to improve fruit setting in blueberries; to advance flowering and increase the yield of strawberries; and also a variety of applications on ornamentals. Application rates up to 80 g/a per application, depending on desired effect.
Compatibility: Incompatible with alkaline materials and solutions containing chlorine.
MAMMALIAN TOXICOLOGY
Oral: Acute oral LD50 for rats and mice >15000 mg/kg.
Skin and eye: Non-irritating to skin and eyes.
Inhalation: No ill-effect on rats subjected to 400 mg/l for 2 h/d for 21 d
Noel: (90 d) for rats and dogs >1000 mg/kg diet (6 d/w).
Toxicity: WHO (a.i.) III (Table 5); EPA (formulation) III
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