12.50; 25, and 75 g a.i.•ha −1 . The growth regulator trinexapac-ethyl did not change the photosynthetic metabolism of plants. However, glyphosate caused damage to the photosynthetic apparatus and a reduction in the carbohydrate concentration and chloroplastid pigments, with casual damage to cell membranes; these effect were more intense at increased doses. The effects of glyphosate were evidenced by the increased concentration of shikimic acid, derived from its mechanism of action. Concludes that, the photosynthetic metabolism of sunflower plants is not affected by the growth regulator trinexapac-ethyl, unlike to the evident effects after application of glyphosate.