Xylem

Question 1

What type of structure is the xylem?

Answer 1

very long, tube-like
Formed from dead cells joined end to end

Question 2

Does the xylem have end walls?

Answer 2

No- uninterrupted tube- allows water to move up easily

Question 3

Thick walls?

Answer 3

Prevents the xylem from collapsing- provides mechanical strength

Question 4

What are the cell walls made out of?

Answer 4

Lignin and cellulose

Question 5

Spiral thickening?

Answer 5

Increasing the flexibility- allowing it to withstand higher water pressures

Question 6

Lignin (waterproofing)?

Answer 6

Water stays in xylem

Question 7

Are the xylem vessels dead or alive?

Answer 7

Dead- leaves a hollow tube for the flow of water

Question 8

Water movement in roots- active transport of mineral ions?

Answer 8

The active transport of mineral ions into the root hair cells increases the rate of water movement as this decreases the water potential of the root hair cells- increased rate of osmosis

Question 9

What is the endodermis?

Answer 9

A waterproof strip of cell walls
Forces all water through the cytoplasm

Question 10

What is the function of the endodermis?

Answer 10

Controls which mineral ions enter the xylem for transport around the plant
Needs transport proteins in endodermis and cell membrane to leave cell wall pathway into cell

Question 11

Revise potometer practical!

Question 12

4 adaptions of the xylem?

Answer 12

No cytoplasm- easier flow of water
Long cells with no end walls for continuous flow of water
Lignin to withstand tension and for waterproofing
Pits in walls allow lateral movement

Question 13

Sunken stomata?

Answer 13

Reduce water loss as there is a reduced rate of transpiration
High humidity in the pit reduces the water potential gradient- less transpiration