Stem abscission in Crassula argentea: Cell separation and inter-tissue signalling in response to ethylene.

摘要

Stem abscission of the jade plant, Crassula argentea Thunb., in response to ethylene was studied first by establishing the anatomical aspects of the process during cell separation. Light microscopy showed that the separation layer was formed by cell proliferation and when this layer was separated and its surface examined with the scanning electron microscope, the cells were observed to be torn apart, leaving collapsed walls. Transmission electron microscopy revealed that, at the site of the newly forming walls, the cells contained abundant cellular organelles.;Secondly, breakstrength of explants was determined using a probe attached to an Instron stress strain analyzer. The decline in breakstrength of explants incubated with ethylene over time was associated with the increase in abscission and development of the separation layer.;Finally, experiments with dissected explant segments showed that there was no enhanced response to ethylene by segments without a stele. This suggests that the stele plays an important role in signalling processes during Crassula stem abscission.