The Effect of Temperature on Rate of Ethylene Evolution from Ethephon and from Ethephon-treated Leaves of Sour Cherry1

Abstract

The effect of temperature on ethylene evolution from ethephon-treated sour cherry ( Prunus cerasus L. cv. Montmorency) leaves was determined subsequent to foliar application. The upper surface of uniform fully expanded leaves was treated in the field with 125 μ g of ethephon, (2-chloroethyl)phosphonic acid. After 24 hours, leaves were detached and ethylene was measured during incubation at temperatures between 10 and 34°C. Ethephon degradation in buffered solutions was also monitored between 10 and 50° and over a range in pH from 3.0 to 7.0. The effect of temperature on rate of endogenous ethylene evolution was examined for sweet cherry shoots and sour cherry leaves, and was calculated for several other tissues and species from values found in the literature. The rate of ethylene evolution from both ethephon-treated leaves and buffered solutions was markedly temperature dependent, with an apparent energy of activation (E a ) of 30 to 32 kcal mole -1 . There was no pH-temperature interaction affecting the E a for buffered solutions. A generalized E a for endogenous ethylene evolution was about 13 kcal mole -1 .