xylem

[malamy at mcclb0.med.nyu.edu]

I'm looking for some information about xylem differentiation.  Does anyone
know of literature describing the mechanism by which xylem cells proceed
from lignification to rigidification to lysis?  What are the signals for
the transition between the stages?  Can cells stop at one stage, or are 
they committed from the beginning to lysis?  Any references would be
appreciated.     Thanks Laura