Plant growth regulator containing a phthalimide derivative

A method of regulating plant growth, which comprises applying an effective amount of a substituted dicarboxylic acid derivative having the formula:

• ##STR29## wherein R.sup.1 and R.sup.2 are, same or different, a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a C.sub.1 -C.sub.3 alkyl group or together represent a C.sub.3 -C.sub.5 alkylene group or a divalent organic group represented by the formula, --CH.dbd.CH--CH.dbd.CH--, optionally substituted by X.sub.n to form a cyclic group;
• R.sup.3 is a hydrogen atom or a C.sub.1 -C.sub.3 alkyl group;
• and R.sup.4 is a cyano group or a group represented by the formula, --COOR.sup.5, --CH.sub.2 COOR.sup.5 or --CONR.sup.6 R.sup.7, in which X is, same or different, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a C.sub.1 -C.sub.4 alkyl group, a C.sub.1 -C.sub.4 alkoxy group, a hydroxyl group, a nitro group or an amino group and n is 0, 1, 2, 3, or 4, R.sup.5 is a hydrogen atom or a C.sub.1 -C.sub.6 alkyl group, R.sup.6 and R.sup.7 are, same or different, a hydrogen atom, a C.sub.1 -C.sub.4 alkyl group or together represent a C.sub.3 -C.sub.5 alkylene group optionally substituted by a methyl group, or physiologically acceptable metal salts or amine salts thereof.

A substituted dicarboxylic acid derivative having the formula:

• ##STR30## wherein R.sup.1 and R.sup.2 are, same or different, a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a C.sub.1 -C.sub.3 alkyl group or together represent a C.sub.3 -C.sub.5 alkylene group or a divalent organic group represented by the formula, --CH.dbd.CH--CH.dbd.CH--, substituted by X.sub.n to form a cyclic group;
• R.sup.3 is a hydrogen atom or a C.sub.1 -C.sub.3 alkyl group;
• and R.sup.4 is a cyano group or a group represented by the formula, --COOR, --CH.sub.2 COOR.sup.5 or --CONR.sup.6 R.sup.7, in which X is, same or different, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a C.sub.1 -C.sub.4 alkyl group, a C.sub.1 -C.sub.4 alkoxy group, a hydroxyl group, a nitro group or an amino group and n is 1, 2, 3 or 4, R.sup.5 is a hydrogen atom or a C.sub.1 -C.sub.6 alkyl group, R.sup.6 and R.sup.7 are, same or different, a hydrogen atom, a C.sub.1 -C.sub.4 alkyl group or together represent a C.sub.3 -C.sub.5 alkylene group optionally substituted by a methyl group, or physiologically acceptable metal salts or amine salts thereof.