A hollow tube made up of dead tissue- allows water to be transported up against gravity
Has lignin in walls- strengthen and waterproof the xylem to withstand water's high pressure
Pits of non-lignified areas: allow water to be transferred in and out of the xylem
What is the role of the xylem?
Transporting water and minerals from roots to leaves- around the plant
How is water initially moved up from the roots?
Root pressure- allows water to move up and due to water molecules being adhesive, they stick together and move up
How is water moved up the xylem ?
Due to evaporation, water moves up the plant. Since it is adhesive, it sticks to the lignin in the cell walls and due to it being cohesive, all the molecules move up together
What is the transpiration stream?
Constant evaporation under the leaves through the stomata pulling up a stream of water through the xylem
How are xylem vessels made?
Lignin in the cell wall restricts entry of water and solutes
Autolysis of cell contents- organelles are broken down by enzymes
End walls between cells become broken down
Dead cells form a column
A hollow tube of xylem cells is made with pits on the side
