The invention describes a compound having the formula (I): wherein X is F, Cl, Br, or I; R 1 is CH 3 , C 2 H 5 , C 2 H 4 R 3 , C 2 H 3 R 3 R 4 , C 3 H 7 , C 3 H 6 R 3 or C 3 H 5 R 3 R 4 ; R 2 is H, CH 3 , C 2 H 5 , C 2 H 4 R 3 , C 2 H 3 R 3 R 4 ; and R 3 and R 4 are, independently, X, OH or NH 2 . Compounds are used for increasing plant growth.