PURPOSE: To obtain a compound having growth-inhibiting activity of plants and long-term germination-inhibiting activity of plants and useful as a plant growth regulator.

CONSTITUTION: An abscisic acid derivative is expressed by formula I. The compound of formula I is obtained by reacting a compound of formula II with N-bromosuccinimide and benzoylperoxide and then, reacting the reactional product with quinoline, adding rose bengal thereto, stirring these substances under oxygen atmosphere, dissolving a reacted liquid in methanol, absorbing the solution into a basic alumina, suspending the liquid in hexane to give a compound of formula III, adding 1N sodium hydroxide aqueous solution to the compound of formula III, stirring the liquid and separating the abscisic acid derivative. Abscisic acid is a sort of plant hormone and retains storing and life-prolonging effect of seeds and nutrient growth period of a plant and yield-increasing effect on plants can be expected by the abscisic acid derivative.