Effect of calcium, (2-chloroethyl) phosphonic acid and ethylene on bean leaf abscission

Summary The effects of CaCl₂, (2-chloroethyl) phosphonic acid (Ethephon) and ethylene on leaf abscission of debladed and intact bean plants (Phaseolus vulgaris L.) were studied. Ethephon (1000 g/l) and ethylene (8 l/l) induced abscission in debladed and intact plants in 24–72 h whereas IAA (10^-5M), cycloheximide (10^-5M) and CaCl₂ (0.068M) delayed abscission in debladed plants. CaCl₂ completely inhibited the abscission-enhancing effect of Ethephon in intact bean leaves. When CaCl₂ and Ethephon were applied simultaneously to separate halves of the leaf blade, leaves with Ethephon applied closest to the pulvinus abscised rapidly; when CaCl₂ was applied closest to the pulvinus, abscission was prevented. Calcium pre-treatment prior to ethylene (8 l/l) treatment of debladed plants delayed abscission as compared to those treated with ethylene alone.Michigan Agricultural Experiment Station Journal Article No. 6299.