Structures and functions of xylem

What are the 2 functions of the xylem?

Transport of water and mineral ions and support

What is parenchyma?

Around the xylem and gives it thick walls, stores food and contains tannin deposits

What is tannin?

bitter, astringent-tasting chemical that protects plants from herbivore attack

What are xylem fibres?

Long cells with lignified secondary walls that provide mechanical strength (don’t transport water)

What is lignin?

Can form rings, spirals or relatively solid tubes with small undignified areas called bordered pits (where water leaves xylem)

What do lignified cell walls do?

Add strength to withstand the hydrostatic pressure so vessels don’t collapse, impermeable to water

What do no end plates mean?

Allows the mass flow of water and dissolved solutes as cohesive and adhesive forces are not impeded

What does no protoplasm mean? (cells are dead when mature)

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

What do pits in wall (non-lignified sections) mean?

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

What does small diameter of vessels mean?

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