Gas exchange - plants

Question 1

What is the primary function of leaves in plants?

Answer 1

Gas exchange

Question 2

What three types of tissues are found in a leaf?

Answer 2

• Epidermal tissue
• Mesophyll tissue
• Vascular tissue

Question 3

What forms the outer boundary of the leaf?

Answer 3

Epidermal tissue

Question 4

What is the role of the mesophyll tissue in leaves?

Answer 4

It makes up the bulk of the internal structure of the leaf and is where photosynthesis occurs.

Question 5

What is the function of vascular tissue in leaves?

Answer 5

Transport of substances between the leaf and the rest of the plant

Question 6

What are stomata?

Answer 6

Tiny pores in the lower epidermis that allow for gas exchange

Question 7

What surrounds each stoma and controls its opening and closure?

Answer 7

Guard cells

Question 8

What happens to guard cells when water moves into them?

Answer 8

They become turgid and open the stomata

Question 9

What is the cuticle in leaves?

Answer 9

A waxy layer that forms an impermeable barrier

Question 10

What are the two types of mesophyll tissue?

Answer 10

• Palisade mesophyll
• Spongy mesophyll

Question 11

Where is palisade mesophyll located and what is its function?

Answer 11

Beneath the upper epidermis; it contains many chloroplasts for maximum photosynthesis

Question 12

What is the role of spongy mesophyll?

Answer 12

Contains large air spaces and increases the surface area for gas exchange

Question 13

What do xylem vessels transport?

Answer 13

Water and mineral ions from the roots to the leaves

Question 14

What do phloem vessels transport?

Answer 14

Products of photosynthesis from the leaves to other parts of the plant

Question 15

What is transpiration?

Answer 15

The loss of water vapour through stomata during gas exchange

Question 16

What is a consequence of gas exchange in leaves?

Answer 16

Transpiration

Question 17

True or False: Stomata are open all the time for gas exchange.

Answer 17

False

Question 18

What is one advantage of transpiration for plants?

Answer 18

It provides cooling via evaporation

Question 19

What factors affect the rate of transpiration?

Answer 19

• Air movement
• Temperature
• Light intensity
• Humidity

Question 20

How does air movement affect transpiration?

Answer 20

Increased air movement leads to higher rates of transpiration

Question 21

What happens to transpiration rates at very high temperatures?

Answer 21

They slow down as stomata close to prevent excess water loss

Question 22

How does light intensity affect transpiration?

Answer 22

Higher light intensity increases transpiration until stomata are fully open

Question 23

What effect does high humidity have on transpiration?

Answer 23

It reduces the rate of transpiration

Question 24

What is a potometer used for?

Answer 24

To measure the rate of transpiration indirectly by measuring water uptake

Question 25

What does a bubble potometer measure?

Answer 25

The movement of an air bubble along a water-filled tube

Question 26

What does a mass potometer measure?

Answer 26

The change in mass of a water-filled test tube connected to a plant shoot

Question 27

What environmental factors can be varied to measure transpiration?

Answer 27

* Wind speed * Humidity * Light intensity * Temperature

Question 28

When controlling variables in transpiration experiments, what should be kept constant?

Answer 28

Any variables other than the one being investigated

Question 29

What is the function of the waxy cuticle?

Answer 29

Prevents gases and water vapour from leaving through the epidermis so that gas exchange must occur through stomata. This allows gas exchange and water loss to be controlled

Question 30

What is the function of the epidermis?

Answer 30

Contain stomata for gas exchange. Most stomata are found in the lower epidermis where the temperature is lower. This reduces water loss

Question 31

What is the function of air spaces in the leaf?

Answer 31

Maintains a concentration gradient of gases between the air and spongy mesophyll cells by allowing movement of gases

Question 32

What is the function of the guard cells?

Answer 32

Control gas exchange and water loss by opening or closing stomata

Question 33

What is the functions of veins in the leaf?

Answer 33

Xylem vessels bring water to the leaf which is required for photosynthesis and transpiration. Photosynthesis requires carbon dioxide to diffuse into the leaf while transpiration involves the loss of water vapour