Salicylic acid changes activities of H2O2-metabolizing enzymes and increases the chilling tolerance of banana seedlings

Pretreatment in the chilling-sensitive banana seedlings by spraying 0.5 mM salicylic acid (SA) hydroponic solution onto leaves and irrigating to roots at 30/22 degreesC for 1 day induced an increase of chilling tolerance during subsequent 5 C chilling stress. Pretreatment of 0.5 mM SA treatment at 30/22 degreesC for 1 day did not result in a remarkable change in superoxide dismutases (SOD) activity, but reduced catalases (CAT) and ascorbate peroxidase (APX) activities, and increased peroxidases (POX) activity. During a 5 degreesC chilling stress period, however, SA pretreatment caused an activation of SOD, CAT and APX activities, while it did not change POX activity. Different effects of SA on protective enzyme activities could be associated with hydrogen peroxide (H2O2) metabolism. Measurement of H2O2 levels and staining with diaminobenzidine (DAB) indicated that SA pretreatment at 30/22 degreesC resulted in H2O2 accumulation; however, during subsequent 5 degreesC chilling stress, SA pretreatment reduced H2O2 overproduction. The results suggested that H2O2 metabolism could participate in enhanced chilling tolerance of SA in banana plants. (C) 2002 Elsevier Science B.V. All rights reserved.