Apocynin was used as an inducer of nitric oxide (NO) synthesis in leaves of two maize (Zea mays L.) cultivars (SHS 3031 and DKB 240). The transcription of γ-glutamylcysteine synthetase (γ-ecs), glutathione synthetase (gshs), chalcone synthase (chs), flavanone 3-β-hydroxylase (fht1), glutathione S-transferase (gst23), ascorbate peroxidase (apx1, apx2), catalase (cat1, cat3), and superoxide dismutase (sod2) genes were quantified in leaves of maize and NO presence was detected by fluorescence microscopy. An increase in the fluorescence after apocynin treatment was not observed in leaves of DKB 240 but leaves of SHS 3031 showed higher fluorescence after 6 and 12 h of apocynin treatment. We observed that γ-ecs, apx1, cat1, and sod2 transcription increased after 24 h of apocynin treatment in SHS 3031.