Induction of Garlic Glutathione S-Transferase by the Herbicide Oxadiazon

The application of the herbicide oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-5-one] to garlic (Allium sativum) resulted in a progressive increase in glutathione S-transferase (GST) activity across various plant tissues, including seedlings, roots, shoots, leaves, and stems. The lowest concentration of oxadiazon that induced a discernible increase in GST activity was 0.025 ppm. The maximal enzyme activity observed was more than 275% of the control values at oxadiazon concentrations ranging from 10 to 20 ppm. In eight-day-old garlic plants, a significant elevation in enzyme activity in the shoots occurred after 6 hours of exposure, with peak activity observed between 24 to 26 hours. Comparable but reduced increases in GST activity were recorded in the shoots of broad bean (Vicia faba) and corn (Zea mays). However, no significant change in enzyme activity was detected in lentil (Lens esculenta), bitter vetch (Vicia ervilia), wheat (Triticum aestivum), or barley (Hordeum vulgare) following oxadiazon treatment.