Effects of Abscisic Acid,Salicylic Acid,Ethylene and Hydrogen Peroxide in Thermotolerance and Recovery for Creeping Bentgrass

Abscisic acid (ABA), salicylic acid (SA), ethylene, and hydrogen peroxide (H₂O₂) may be involved in the regulation of plant responses to heat stress. The objective of this study was to determine whether these signaling molecules are involved in survival at high temperatures in creeping bentgrass (Agrostis stolonifera). We investigated the effects of treatment with ABA, SA, H₂O₂, and ACC (an ethylene precursor) on physiological damage occurring in creeping bentgrass during heat stress (35 °C for 1 month). We also compared the effects of chemical application and the induction of thermotolerance using moderate heat stress (30 °C for 24 h). All of the pre-treatments (heat or chemical) resulted in increased tolerance to prolonged heat stress (1 month) compared to control plants. All treated samples showed more green leaves, decreased membrane leakage and reduced oxidative damage compared to control plants. We then measured changes in the endogenous concentration of these chemical components during heat stress (35 °C) and during recovery after a stress treatment (cooling back to 20 °C). An oxidative burst was detected 5 min after the initiation of heat treatment, with the increase in H₂O₂ being detected primarily in the apoplast of the cells in both leaf and root tissues. Free SA was detected only an hour after the initiation of heat stress, and concentration remained low subsequently. Neither ABA nor ethylene concentrations rose during heat stress, but the concentration of both increased during subsequent cooling. These results suggest that the signaling components of interest are involved in thermotolerance in creeping bentgrass, but that the different chemicals are likely to be involved in separate signaling pathways. An oxidative burst and SA may be bona fide heat stress signals, but ABA and ethylene appear to be involved in signaling pathways in response to recovery from heat stress in this species.