Abscission: The Phytogerontological Effects of Ethylene

The role of ethylene in the aging of bean Phaseolus vulgaris L. cv. Red Kidney petiole abscission zone explants was examined. The data indicate that ethylene does accelerate aging in addition to inducing changes in break strength. Application of ethylene during the aging stage stage 1 promoted abscission when followed by a second ethylene treatment during the cell- separating stage stage 2. The half-maximal effective concentration of ethylene to induce aging was about 0.3 ppm 10 ppm was a saturating dose. CO2 reversal of ethylene action during stage 1 was incomplete and gave ambiguous results. The possibility that ethylene not only accelerated aging but that it was also a requirement for it was also tested and experimental evidence in favor of this idea was obtained. It was concluded that ethylene plays a dual role in the abscission of bean petiole explants a phytogerontological effect and a cellulase-inducing effect.