Tylose

As Verthyllung is defined as the closure of disused tracheae especially in angiosperms.

In the wood of angiosperms ( Angiospermae ), there are wide large bore vessels for water transport. In the course of secondary growth of the shoot it from the growth layer ( cambium ) are always re- created. The tracheae further inside are therefore no longer actively involved in the transport of water and are no longer needed by the plant.

Therefore, the plant closes these vessels by the formation and placement of a sac-like protrusion of an adjacent parenchymal cell ( Thylle ) within the trachea. The connection between the trachea and parenchymal Tüpfelkanäle between the adjacent cells are generally used. The newly formed tyloses can turn form their own cell wall and act as an independent cell within the trachea. Your task is then for example the storage of starch.