Xylem and phloem

Question 1

What is the xylem made of?

Answer 1

A tissue made of several different cell types including xylem vessels, xylem parenchyma and xylem fibres

Question 2

What are xylem vessels?

Answer 2

Long tubes that carry water and mineral ions

Question 3

What is the name for a singular xylem vessel cell?

Answer 3

A xylem vessel element

Question 4

What are xylem vessels made of?

Answer 4

Columns of dead cells fused end-to-end

Question 5

What are xylem vessels like before they mature?

Answer 5

Elongated living cells

Question 6

What happens as xylem vessels mature?

Answer 6

They end wall breaks down, cytoplasm disappears and the cellulose cell walls become thickened with lignin

Question 7

What is the effect of lignin?

Answer 7

It causes cell contents to die and the end wall of each cell disappears

Question 8

What is the function of lignin?

Answer 8

To strengthen and reinforce the walls of the xylem vessels so they don’t collapse under transpiration pull

Question 9

What are the types of lignin thickening?

Answer 9

Spirals, rings or relatively unbroken tubes of lignin which has pits

Question 10

What is the purpose of pits?

Answer 10

So water can pass sideways into other cells of the plant of to other xylem vessels if one becomes blocked

Question 11

What are xylem parenchyma?

Answer 11

Thick walled cells

Question 12

What is purpose of xylem parenchyma?

Answer 12

They pack around xylem vessels for support and store food

Question 13

What do xylem parenchyma contain?

Answer 13

Tannin which is bitter tasting

Question 14

What is the purpose of tannin?

Answer 14

To protect plants from herbivores

Question 15

What are xylem fibres?

Answer 15

Long cells with lignified secondary walls

Question 16

What is the purpose of xylem fibres?

Answer 16

Provide extra mechanical strength for support but don’t transport water

Question 17

What are the types of cells in the phloem?

Answer 17

Sieve tube elements and companion cells

Question 18

Where are sugars made by photosynthesis stored?

Answer 18

Roots, leaves, seeds and fruits

Question 19

How are sugars transported?

Answer 19

As sucrose which are dissolved in water to form sap

Question 20

What is the pressure in the phloem?

Answer 20

2000 kPa

Question 21

What do sieve tube elements form?

Answer 21

A tube to transport sugars

Question 22

What are sieve tube elements?

Answer 22

Living cells which are mainly cytoplasm which are lined up end to end to form tubes

Question 23

What is the shape of sieve tubes?

Answer 23

They are thin walled and are 5/6 sided

Question 24

What do sieve tube elements contain?

Answer 24

Perforated cross walls called sieve plates

Question 25

What is the purpose of sieve plates?

Answer 25

They allow phloem contents to flow

Question 26

What is the result of pores in size plates developing?

Answer 26

Tonoplast and organelles break down so nucleus dissapears

Question 27

What are companion cells?

Answer 27

Small cells that lie between sieve tubes

Question 28

What is the structure of companion cells?

Answer 28

Large nucleus, dense cytoplasm and numerous mitochondria

Question 29

What is the function of companion cells?

Answer 29

Complete metabolic processes for both companion and sieve tube so very metabolically active living cells

Question 30

What is an example of metabolic process completed by companion cells?

Answer 30

Produce ATP for loading sucrose into sieve tubes (active transport)

Question 31

How are sieve tubes and companion cells linked together?

Answer 31

By plasmodesmata to exchange materials

Question 32

What are other phloem tissues?

Answer 32

Sclereids and fibres

Question 33

What are sclereids?

Answer 33

Cells with extremely think cell walls

Question 34

What is the function of sclereids and fibres?

Answer 34

To support