Problem to be solved: to provide a novel root system promoter.Problem to be solved: to provide a plant root forming promoter including saturated or unsaturated fatty acid or a salt of 16 to 18 carbon atoms.No selection【課題】新規な根系形成促進剤を提供する。【解決手段】炭素数16~18の飽和もしくは不飽和脂肪酸、またはその塩を含む、植物の根系形成促進剤を提供する。【選択図】なし