Impact of postharvest brassinosteroids treatment on PAL activity in tomato fruit in response to chilling stress

Tomatoes, as originally tropical fruits, cannot easily be stored at low temperatures, due to the risk of chilling injury (CI). To develop an effective technique to reduce CI, the effects of treatments with 0, 3 and 6 mu M brassinosteroids (BRs) on chilling injury, electrolyte leakage, malondialdehyde (MDA), proline and total phenol contents, and phenylalanine ammonia-lyase (PAL) activity were investigated in tomato fruits stored at 1 degrees C for 21 days. The chilling injury, electrolyte leakage and malondialdehyde content were significantly reduced by brassinosteroids treatments especially at 6 mu M. Also, fruits treated with BRs exhibited significantly higher total phenol and proline contents as compared with the control fruits. Our results indicate that during storage time fruits treated with BRs exhibited significantly higher PAL activity. These results suggest that BRs treatment protects tomatoes from CI by enhancing total phenol and proline contents and reducing MDA content, and thus maintaining membrane integrity. (C) 2012 Elsevier B.V. All rights reserved.