The method of altering the alkaloid composition of a poppy plant comprising the step of applying an effective amount of acylcyclohexanedione compound or agriculturally acceptable salt thereof to said poppy plant or locus thereof. Further, the present invention also provides the method of altering the alkaloid composition of a poppy plant comprising the step of applying an effective amount of methyl jasmonate or agriculturally acceptable salt thereof to said poppy plant or locus thereof.