Gallic acid (GA) alleviating copper (Cu) toxicity in maize (Zea mays L.) seedlings

The aim of this study is to determine the effect of GA on maize seedlings as well as its antioxidative effect under copper (Cu) stress. To that end, maize seedlings were exposed to 1.5 mM GA and 1 mM Cu solutions, and the seedlings were allocated to following experimental groups: 18-hr distilled water (DI) (Control), 6-hr GA + 12-hr DI (GA), 6-hr DI + 12-hr Cu (Cu), 6-hr GA + 12-hr Cu (GA + Cu), 12-hr Cu +6-hr GA (Cu + GA), and 18-hr GA and Cu mixture (GA = Cu). The experiment was designed by randomized block design with three repetitions. The results showed that GA alone and GA + Cu treatments significantly decreased membrane damage and H₂O₂ formation compared to the other treatments. GA formation was determined to be highest in turn in treatments GA + Cu and GA alone. The proline content significantly decreased in treatments GA alone and GA + Cu. The highest catalase (CAT) activity was observed in GA alone application, whereas GA + Cu treatment led to increase in guaiacol peroxidase (GPX), superoxide dismutase (SOD), and ascorbate peroxidase (APX) activities. GA has a protective effect on chlorophyll contents and relative water content (RWC), but not on carotenoid levels under Cu stress. Overall, GA alone application or GA + Cu stress may prevent the formation of reactive oxygen species (ROS) due to chelation effect of GA.