Dr. Sameera Omar Bafeel is a professor in the Department of Biology, from the College of Science, King Abdulaziz University (KAU), Jeddah, Saudi Arabia.
Herbivory by chewing insects causes an oxidative burst, characterized by the production of hydrogen peroxide giving rise to both local and systemic responses. Hydrogen peroxide is well known signaling molecule that can activate the antioxidant system to enhance the plant defense response. In his study, we investigated the relationship between antioxidant responses in tomato and maize after Spodoptera exigua attack and the plant resistance. As an indication for plant resistance, fresh and dry biomass of tomato and maize shoot was determined. All data were collected after 2 hours, 2 days and 7 days following infestation. The results indicated that, shoot fresh and dry weight of tomato significantly decreased lower than control (uninfected plants) under all studied feeding times. On the other hand, maize leaves fresh and dry biomass did not decrease than controls at 2 hours and 2 days after infestation. The infestation significantly increases H2O2 and ascorbic acid concentration in maize leaves at 2 hours and 2 days after infestation while no change recorded in tomato leaves compared to their corresponding controls. Free phenols content significantly increased in infected only in tomato leaves more than control. The infestation significantly enhances the activities of SOD, CAT and APX in maize leaves but had no significant effect on SOD and CAT activity in tomato plant; only APX activity enhanced. In maize, the highest enzymatic activity recorded after 2 days of infestation. The highest APX activity was observed at 7 days after infestation in tomato. Taken together we could conclude that antioxidant system in maize induced and enhance plant defense to Spodoptera exigua infestation.