Biochemical and Photosynthetic Evaluation of Responses in Zea mays L. Under Drought Stress

Antioxidant defense system(s), pigments content and photosynthetic activity as well as some biochemical changes under drought stress were analyzed in maize (Zea mays L. cv. Giza 21) leaves to determine the response of plant to drought stress and to elucidate the role of various protective mechanisms against oxidative stress. It was found that the application of drought stress led to changes in the carbohydrates and protein contents. Total soluble sugars, accumulated in the leaves of water-stressed plants, whereas, starch and protein contents were dropped to a small amounts compared to the control. Furthermore, plants have well-developed defense systems against reactive oxygen species (ROS), involving both limiting the formation of ROS as well as instituting its removal. Within a cell, the activities of a range of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) involved in scavenging ROS were investigated. During dehydration the SOD, APX and CAT increased significantly up to 4 days, then declined in their activities but still maintained higher than the control levels this indicates that the defense systems involved are efficient in the protection of plant cells against oxidation. In addition, there was consistent increase in the lipid peroxidation and accumulation of malondialdehyde (MDA). The levels of hydrogen peroxide were also elevated during stressing periods. In this study we are reporting the negative response of maize plants toward drought stress especially on the antioxidant enzymatic activity for the prolonged drought effect.