The purpose of the present invention is to provide a compound that can regulate growth of plants. A compound selected from the group consisting of (A) and (B) has plant growth regulating activity. (A) 3H imidazo[4 5 d] [1 2 3]triazin 4 6(5H 7H) dione (B) 3 methyl 3H imidazo[4 5 d] [1 2 3]triazin 4 6(5H 7H) dione