An examination of the importance of ethanol in causing injury to flooded plants

Abstract. We have examined the widely held theory that ethanol toxicity is a prime cause of the injury and death of plants in soil flooded with water. The tests were made on peas ( Pisum sativum L.) at the early flowering or fruiting stages, when they are known to be severely injured by flooding.
Supplying ethanol in aerobic or anaerobic nutrient solution at similar concentrations to those we found in flooded soil (up to 3.9 mol m⁻³) or in the xylem sap of flooded pea plants (up to 2.1 mol m⁻³) caused no injury. One hundred times these concentrations gave little extra effect and failed to simulate flooding injury. Isolated leaf protoplasts and detached leaves were also resistant to damage by ethanol at these concentrations.
Other published measurements of ethanol concentrations in flooded plants are similar to or less than those we report for pea plants. Exceptions include root nodules and germinating pea seeds. Reports by others of responses to applied ethanol in a wide variety of circumstances confirm that in flooded plants the amounts are probably too small to explain the observed injury. Alternative mechanisms are discussed.