6.8 Structures of the xylem and phloem

Question 1

Name the two plant transport tissues

Answer 1

Xylem

Phloem

Question 2

What is the function of the xylem?

Answer 2

Transports water and minerals up the
plant, from the roots to the leaves via the
transpiration stream

Question 3

Describe how the xylem is adapted to its function

Answer 3

● Composed of dead cells laid end-to-end to form a long,
hollow, continuous column
● No end walls which provides little resistance to the
passage of water
● Thick cell wall strengthened with lignin to provide support

Question 4

What is the function of the phloem?

Answer 4

Transports sucrose up and down the stem
from photosynthetic tissues (e.g. mature
green leaves) to non-photosynthetic tissues
(e.g. developing seeds) via translocation

Question 5

What are the two cell types that make up the

phloem?

Answer 5

Sieve tube elements

Companion cells

Question 6

Describe how the phloem is adapted to its function

Answer 6

● Sieve tube elements are long, thin cells, laid end-to-end with
perforated end plates to enable the flow of sugars. They contain no
nucleus and little cytoplasm to allow sugars to flow easily.
● Companion cells (adjacent to sieve tube elements) contain a dense
cytoplasm, nucleus and mitochondria. They provide energy for
processes in both cell types.