Abstract: Compositions having a growth regulatory effect, characterized in that they comprise a mixture of a product A, which is mepiquat chloride, and of a derivative of cyclopropylmalonanilic acid (compound B) of formula (I):(R.sup.1).sub.p C.sub.6 H.sub.5-p --NR.sup.2 --CO--C(C.sub.2 H.sub.4)--CO--R.sup.3 --R.sup.4in which:R.sup.1 represents a halogen atom or an alkyl, alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, nitro, cyano or acetyl group, it being possible for these various radicals optionally to be substituted by one or a number of halogen atoms;p is an integer equal to 0, 1, 2 or 3; when there are a number of R.sup.1 radicals, the latter can be identical to or different from one another;R.sup.2 is a hydrogen atom or a lower alkyl group; the qualifier lower denotes a group containing 1 to 4 carbon atoms;R.sup.3 is an oxygen or sulfur atom;R.sup.