PROBLEM TO BE SOLVED: To provide a plant growth regulator.SOLUTION: The plant growth regulator comprises a compound represented by general formula 1, or a salt or ester thereof. [In the formula, (A-A-A-A) is (N=CH-CH=CH) or (NH-CH-CH-CH); Rand Rare each independently H, an alkyl group or a halogen atom; and Ris a hydroxyl group or an alkoxy group.]SELECTED DRAWING: None【課題】植物成長調整剤の提供。【解決手段】一般式1で表される化合物或いはその塩又はエステル体からなる、植物成長調整剤。[(A1-A2-A3-A4)は(N=CH-CH=CH)又は(NH-CH2-CH2-CH2);R1及びR2は各々独立にH、アルキル基又はハロゲン原子;R3=ヒドロキシル基又はアルコキシ基]【選択図】なし