3.3.3 The Xylem

Question 1

What tissues is the xylem made up of?

Answer 1

Tracheids (long, narrow tapered cells with pits)
Vessel elements (large with thickened cell walls and no end plates when mature)
Xylem parenchyma
Sclerenchyma cells (fibres and sclereids)

Most of the xylem tissue is made up of tracheids and vessel elements, which are both types of water-conducting cell

Question 2

What is the function of the lignified cell walls (mature cells)?

Answer 2

Adds strength to withstand the hydrostatic pressure so the vessels do not collapse, impermeable to water.

Question 3

What is the function of no end plates (mature)?

Answer 3

Allows the mass flow of water and dissolved solutes as cohesive (between water molecules) and adhesive (between water and the walls) forces are not impeded.

Question 4

What is the function of no protoplasm (cells are dead when mature)?

Answer 4

Doesn’t impede the mass flow of water and dissolved solutes (transpiration stream).

Question 5

What is the function of pits in the wall (non-lignified sections)?

Answer 5

Lateral movement of water, allows continual flow in case of air bubbles forming in the vessels.

Question 6

What is the function of the small diameter of vessels?

Answer 6

Helps prevent the water column from breaking and assists with capillary action.