Plant Organ System

Question 1

What is the function of the xylem?

Answer 1

The xylem transports water and minerals from the roots up the plant stem and into the leaves.

Question 2

What is the function of the phloem?

Answer 2

The phloem moves sugars that the plant has produced by photosynthesis to where they are needed

Question 3

How are the xylem adapted?

Answer 3

-Lose their end walls so the xylem forms a continuous, hollow tube.
-vessels are strengthened with lignin

Question 4

How are phloem adapted?

Answer 4

-Companion cells - transport of substances in the phloem requires energy. One or more companion cells attached to each sieve tube provide this energy.
-Sieve tubes - specialised for transport and have no nuclei.

Question 5

Describe the role of stomata and guard cells in
leaves.

Answer 5

To enter the leaf, gases diffuse through small pores called stomata. As the stomata open, water is lost by the process of transpiration. Closing the stomata helps to control water loss.

Question 6

How does temperature affect the rate of transpiration?

Answer 6

Increases rate
Increases molecular movement so that: more water molecules evaporate from cell surfaces; the rate of diffusion of water molecules from the leaf is increased

Question 7

How does humidity affect the rate of transpiration?

Answer 7

Decrease rate
Reduces the concentration of water molecules outside the leaf; diffusion of water from the leaf increases

Question 8

How does light intensity affect the rate of transpiration?

Answer 8

Increase rate
Increases the rate of photosynthesis; stomata open so that water diffuses out of the leaf

Question 9

How does air movement affect the rate of transpiration?

Answer 9

Increase rate
Removes water vapour from leaf surfaces; more water diffuses from the leaf