9.1 Xylem and Phloem

Question 1

What type of tissue is the xylem made from?

Answer 1

Non-living

Question 2

What are the 2 main functions of the xylem?

Answer 2

Transport of water and ions + support

Question 3

In what direction does material flow in the xylem?

Answer 3

Up from roots -> leaves and shoots

Question 4

What is the main structure of the xylem?

Answer 4

Xylem vessels

Question 5

What are xylem vessels in terms of their structure?

Answer 5

Long, hollow structures made by columns of cells fused together end to end

Question 6

What are the other 2 tissues associated with the xylem?

Answer 6

1. Thick-walled parenchyma

2. Xylem fibres

Question 7

Where can thick walled parenchyma be found?

Answer 7

Packed around xylem vessels

Question 8

What is the function of thick walled parenchyma?

Answer 8

Store food + contain tannin deposits

Question 9

What is tannin?

Answer 9

Bitter chemical - protects plants from herbivore attack

Question 10

What are xylem fibres?

Answer 10

Long cells w/ lignified secondary walls

Question 11

What is the function of xylem fibres?

Answer 11

Contain lignified secondary walls - provide extra mechanical strength

Question 12

Do xylem fibres transport water? Yes or no

Answer 12

No

Question 13

How can lignin be laid down in the walls of xylem vessels?

Answer 13

Lignin can form rings, spirals or solid tubes, w/ lots of small unlignified areas called bordered pits

Question 14

What are bordered pits? What is their function?

Answer 14

Small, unlignified areas in the lignified walls of the xylem fibres.
Bordered pits = where water leaves the xylem

Question 15

What type of tissue is the phloem made from?

Answer 15

Living

Question 16

What is the function of the phloem?

Answer 16

Transports food in form of organic solutes around plant from leaves, where they’re made via photosynthesis

Question 17

What does the phloem supply cells with?

Answer 17

Sugars + amino acids, needed for respiration + synthesis of molecules

Question 18

What is the direction of the flow of materials in the phloem?

Answer 18

Up and down the plant

Question 19

What are the main transporting vessels in the phloem?

Answer 19

Sieve tube elements

Question 20

What is the structure of sieve tube elements?

Answer 20

Many cells joined end to end, forming a long, hollow structure

Question 21

What’s the difference between xylem vessels and phloem tubes?

Answer 21

Xylem vessels = lignified

Phloem tubes = unlignified

Question 22

What are sieve plates?

Answer 22

Areas between sieve tube elements where walls become perforated, resulting in many gaps + a sieve-like appearance, allowing phloem contents to flow through

Question 23

What are companion cells?

Answer 23

Active cells next found next to sieve tube elements that supply phloem vessels with all their metabolic needs

Question 24

What are sieve tube elements and companion cells linked by?

Answer 24

Plasmodesmata - microscopic channels through cellulose cell walls linking cytoplasm w/ adjacent cells