IntroductionMelon (Cucumis melo L.), an annual diploid plant, is an economically important horticultural crop grown in temperate, subtropical, and tropical regions worldwide. With a total production of 1.7 million tons, Turkey was the second biggest producer after China in 2009. Like many other fruits melon fruits provide a good source of potassium and vitamin C. They are also fat and cholesterol free, high in water content, and are relatively low in calories. Moreover, melons may have an anticlotting action and are also thought to lower cancer and heart disease risk (Lester, 1996).Biotic and abiotic stresses are the most important factors that severely limit plant growth and metabolism (Makbul et al., 2011). Abiotic stress is the primary cause of crop loss worldwide, reducing average yields for most major crop plants by more than 50% (Bray et al., 2000). Moreover, when the usable areas on the earth are classified in view of stress factors, drought stress is one of the most widespread environmental stresses (Arora et al., 2002;Saruhan Güler et al., 2012). Although each stress factor produces its own specific effect on plants, in general all stress conditions can cause an increase in reactive oxygen species (ROS). ROS are recognized as detrimental to biological systems because they cause the oxidation of lipids, proteins, deoxyribonucleic acid, and carbohydrates. Ultimately, toxic levels of ROS cause a chain reaction of cellular oxidation, which results in unhealthy situations and lethality. In addition to the oxidative stress related production, ROS are an inevitable outcome of normal physiological processes, such as glycolysis and photosynthesis (Mittler et al., 2004). Plant antioxidant systems, both enzymatic and nonenzymatic, play an important role in balancing and preventing oxidative damage (Foyer et al., 1994;Baysal Furtana and Tıpırdamaz, 2010). Nonenzymatic antioxidant metabolites include anthocyanin, flavonoids, carotenoids, α-tocopherol, ascorbate (AsA), and reduced glutathione (GSH) (Halliwell, 1987); enzymatic antioxidants consist of superoxide dismutase (