Herbicidal action of clove oil on cucumber seedlings

The herbicidal action of clove oil on cucumber seedlings was characterized under light and dark conditions. Paraquat showed herbicidal activity only under the light condition, whereas the clove oil displayed herbicidal activity in both the light and the dark condition. Specifically, wilting and water content reduction progressed rapidly under both the light and the dark condition 1 h after the clove oil treatment, whereas the paraquat damage occurred only under the light condition 5 h after treatment. The malondialdehyde concentration increased more with the clove oil treatment than with the paraquat treatment under the light and dark conditions. The superoxide dismutase (SOD) activity was stimulated, but the catalase activity decreased in the clove oil treatment. In contrast, both the SOD and catalase activity decreased in the paraquat treatment. These results suggest that clove oil exerts herbicidal effects through a mechanism that is different from that of paraquat.