Keywords: ABA, abscisic acid; a.i., active ingredient; ANOVA, analysis of variance; DF, diflufenican; DXP, 1-deoxy-d-xylulose; DXR, 1-deoxy-d-xylulose reductoisomerase; ESI–MS, electrospray ionization mass spectrometry; HPLC, high-performance liquid chromatography;