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The effects of foliar application of 24-epibrassinolide (EBR) on chlorophyll content, oxidative damage, and antioxidant capacity in eggplant (Solanum melongena L.) seedlings during a short-term chilling stress and subsequent recovery were investigated. The eggplant seedlings pretreated with 0.1 μM EBR were exposed to 5 °C for 12 h in the dark and then recovered under a normal temperature for another 12 h. The results show that EBR alleviated a chilling-induced oxidative stress reflected by a decrease in malondialdehyde and H2O2 content, O2 .- production rate, and an increase in chlorophyll content and activities of superoxide dismutase, guaicol peroxidase, and catalase. The EBR pretreatment also promoted activities of ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, as well as the accumulation of ascorbic acid (AsA) and glutathione (GSH) involved in the AsA-GSH cycle. Moreover, after the12 h recovery, EBR plus chilling treated leaves showed no significant changes in content of MDA and chlorophyll a, lower reactive oxygen species (ROS) content, and greater activities of AsA-GSH cycle enzymes than in seedlings only chilled. The results suggest that EBR alleviated an oxidative damage caused by the dark chilling stress and accelerated a recovery rate mainly through increasing the ROS scavenging system including the AsA-GSH cycle.

This study was carried out to understand the mechanism of protection of plants under cold stress by exogenous 24-epibrassinolide (EBR). The eggplant (Solanum melongena L.) seedlings were pretreated with five concentrations of EBR (0, 0.05, 0.1, 0.2 and 0.4 °M) and then exposed to day/night temperatures of 10/5 °C for 8 d. The results show that EBR, especially 0.1 °M EBR, dramatically alleviated growth suppression and a decrease in chlorophyll content and photosynthetic rate caused by the cold stress. In addition, EBR also decreased malondialdehyde content and O2 .- production rate induced by the cold stress, and increased the activities of superoxide dismutase, guaiacol peroxidase, catalase, and ascorbate peroxidase, and proline content. The results of the present study suggest that exogenous EBR could improve cold tolerance of eggplant by regulating photosynthesis and antioxidative systems.

The effects of exogenous 24-epibrassinolide (EBR) on the growth, oxidative damage, antioxidant system and ion contents in eggplant (Solanum melongena L.) seedlings under salt stress were investigated. Eggplant seedlings were exposed to 90 mM NaCl with 0, 0.025, 0.05, 0.10 and 0.20 mg dm-3 EBR for 10 d. EBR, especially at concentration 0.05 mg dm-3, alleviated growth suppression caused by NaCl stress, decreased electrolyte leakage, superoxide production and content of malondialdehyde and H2O2 in NaCl-treated plants. EBR also increased activities of superoxide dismutase, guaiacol peroxidase, catalase and ascorbate peroxidase and the contents of ascorbic acid and reduced glutathione. Furthermore, we also found that Na+, Cl- contents were decreased, K+, Ca2+ contents and K+/Na+, Ca2+/Na+ ratios were increased in the presence of EBR under salt stress.