Ancymidol foliar spray at 66 and 132 mgliter1 a.i. significantly decreased height, node number, leaf area, fresh weight, and dry weight of four sunflower cultivars. Ancymidol resulted in darker green leaves and increased chlorophyll content per unit area, as measured spectrophotometrically, when compared with controls. However, chlorophyll
a, b, and total chlorophyll were increased in only two cultivars when measured on a weight basis using high-performance liquid chromatography (HPLC). Ancymidol increased three xanthophyll levels (neoxanthin, vio-laxanthin, and lutein) in the four cultivars, but had no effect on -carotene when measured on a weight basis by HPLC. Chemical name used: a-cyclopropyl-a-(4-methoxyphenyl)-5-pyrimidine methanol (ancymidol).