XYLEM
Consists of vessels and tracheids.
Xylem vessel
Types of lignification
Found in angiosperms (flowering plants).
They are elongated cylindrical cells placed end to end.
Lack a nucleus and protoplasm hence said to be a dead (non-living) tissue.
Have lignified walls to prevent them from collapsing and offer support for the plant.
Have walls perforated with pits to allow passage of water into and out.
Xylem tracheids
Found in gymnosperms.
Are five or six sided cells that are dead and lignified to offer support to the plant.
They are placed end to end.
Have tapered end walls and have pits to allow communication with adjacent cells.
Presence of cross-walls makes them less efficient for transport of water.
Question
- State two ways in which the xylem is adapted to their function.
- Lignified walls to prevent collapsing during water transport.
- Narrow lumen to facilitate capillarity
- Lack cross walls to allow continuous flow of water.
- Have bordered pits to allow lateral movement of water and mineral salts.
- State two differences between xylem tracheids and xylem vessels
|
Xylem Vessels |
Xylem Tracheids |
|
Lack cross-walls |
Has cross-walls |
|
cylindrical shaped |
5 or 6 sided |
