Use of fused ring cyclopentanones and cyclopentenones in controlling plant growth

A method of inhibiting plant growth of a compound formula II

• in which either the pair of symbols X and Y or the pair of symbols Y and Z, together with the carbon atoms to which they are attached, form a non-aromatic ring system having either 5 or 7 ring atoms, all of which are carbon except that one may be oxygen, and which is substituted or unsubstituted, R1 represents a hydrogen atom or an alkyl or a substituted or unsubstituted phenyl group and either R2 represents a hydrogen atom and R3 an alkyl carboxymethyl group, in which case the ring shown in formula II is a cyclopentanone ring, or R2 and R3 together form a double bond, thus forming a cyclopentenone ring, and thereafter any unsatisfied valencies of ring carbon atoms of the cyclopentanone or cyclopentenone ring are satisfied by hydrogen atoms.