Sethoxydim, a commercially available cyclohexanedione class herbicide by targeting the enzymatic activity of acetyl-coenzyme A carboxylase, has been found to moderately inhibit the activity of 4-hydroxyphenylpyruvate dioxygenase, a key enzyme iii the biosynthesis of plastoquinones and tocopherols in plants. (C) 1999 Elsevier Science Ltd. All rights reserved.