In differentiating xylem cells a prima facie case is made for the following cytoplasmic events to occur:

  • 1
    Production of vesicles from dictyosomes and endoplasmic reticulum, and probable guidance of these vesicles to the wall by microtubules.
  • 2
    Secondary formation of multivesicular bodies from dictyosome-derived vesicles, which also move to the plasmalemma and fuse with it.
  • 3
    Passage of single vesicles across the plasmalemma to form lomasomes.
  • 4
    Evagination of the plasmalemma to form plasmalemmasomes.
  • 5
    Formation of myelin-like bodies by the endoplasmic reticulum.
  • 6
    The fusion of vesicles and vacuoles with each other.

These processes are thought to be associated in general with the formation and separate transport of different wall precursors and enzymes to their appropriate sites and, possibly, with the management of synthetic by-products.