Effects of Ethanol on Membrane Integrity and Enzyme Expression in Chilled Cucumber Seedlings

Abstract

Previous experiments have shown that chilling-stressed cucumber seedlings treated with ethanol have greater chilling tolerance when compared to untreated seedlings. To determine whether this increased chilling tolerance would diminish with time after treatment, cucumber seedlings were treated with ethanol and placed at chilling temperatures for 0, 2, 4, 6, or 8 hours after ethanol treatment. Ethanol-induced chilling tolerance declined as the time interval between treatment and chilling exposure increased. A second ethanol treatment was given 3 hours after the first treatment in an attempt to extend the enhanced chilling tolerance response. Ethanol has been reported to function as an anesthetic in some systems, interacting with cellular membranes. To determine the effect of ethanol and chilling on membrane integrity, a malondialdehyde assay was used. Since chilling stress effects may result from accumulation of active oxygen species, the activity of one radical scavenging enzyme (catalase) has been assayed. Ethanol treatment resulted in a rapid increase in catalase activity, and was associated with increased chilling tolerance. The effect of a second ethanol treatment will be discussed as related to induced chilling tolerance, membrane effects, and catalase activity.