The effect of 4-methylbenzenesulfonic acid (4-MBSA) and its binary complexes with Fe (III) and Cu (II) at pH 5.0 and 8.00 on plant growth of Brassica nigra L. (black mustard) were studied. Plant growth was decided by measurement of different growth parameters. The data obtained was used to know whether 4-methylbenzenesulfonic acid and its complexes are plant growth regulating