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LAYERING
Layering - a propagation technique where roots are formed prior to the stem being removed 
                     from the parent plant.

 

PRINCIPLE OF LAYERING
In layering, one must wound the stem such that phloem, but not xylem, translocation is disrupted. The internal anatomy of dicot, gymnosperm and monocot stems dictates the "ideal" type cut that is made to get maximum disruption of translocation in the phloem, while causing minimum disruption of translocation in the xylem.  If done properly, roots form on the stem at the wounded site.  The stem is then cut-off with the attached roots.

 

ANATOMICAL BASIS FOR THE TYPE CUTS USED IN LAYERING

Woody Dicots and Gymnosperms
A ring of bark is removed from around the stem.  The phloem and cambium are attached to the inside of the bark, so when the bark is removed the phloem is also removed.  This leaves the central cylinder of xylem and upward water flow unaffected.

  
Monocots
Monocots have scattered vascular bundles, therefore, it is not possible to cut the phloem and not the xylem.  As a compromise, a slit is cut about 1/3 way into the stem.  This cuts enough of the vascular bundles to disrupt sufficient phloem translocation while still allowing sufficient water flow in the xylem.