The evolution of multicellular plants involved the modification of different cells to perform distinct functions. Part of the success of land plants was based upon the evolution of a very strong molecule called lignin. In this laboratory you will learn how to identify three lignified cells.
1.Tracheids: first to evolve, combined the functions of support and water transport.
2.Vessel elements: subsequently evolved from tracheids, specialized for water transport.
3.Fibers:also evolved from tracheids, cells specialized for support only.
All three can be found in xylem, while fibers can be found in xylem, phloem, and other parts of the plant. The three types of lignified cells are illustrated on the right.