Exogenous 6-benzylaminopurine confers tolerance to low temperature by amelioration of oxidative damage in eggplant (Solanum melongena L.) seedlings

Low temperature is one of the primary constraints to plant production in many parts of the world. It is known that cytokines are involved in the regulation of plant abiotic stress tolerance/adaptation. In this study, the influence of 10 mu M 6-benzylaminopurine (6-BA), a synthetic cytokinin, on the growth, oxidative damage, antioxidant defense system and osmoregulation responses of eggplant (Solanum melongena L.) seedlings were studied under low temperature (10/5 degrees C) stress. Exogenous application of 6-BA significantly ameliorated low-temperature-caused decreases in plant growth and chlorophyll content. 6-BA also alleviated low temperature-induced oxidative damage reflected by decreases in reactive oxygen species (ROS) levels and lipid peroxidation and increases in the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT). Importantly, 6-BA treatment further promoted activities of ascorbate peroxidase (APX) and glutathione reductase (GR), as well as the accumulation of ascorbic acid (AsA) and glutathione (GSH) involved in the AsA-GSH cycle during low temperature stress. Furthermore, 6-BA treatment greatly enhanced the contents of proline and soluble protein under low temperature. From these results, it can be concluded that 6-BA can play a positive role in the alleviation of oxidative damage caused by ROS overproduction through enhancing antioxidant defense system, resulting in improving the low-temperature tolerance.