1.8 and 1.9 Exchange In Plants/Transpiration

Question 1

What controls the size of the stomata?

Answer 1

The guard cells which surround them

Question 2

Name 2 gases diffused by plants in and out of the stomata

Answer 2

• oxygen: needed for respiration and is a waste product of photosynthesis
• carbon dioxide: needed for photosynthesis and is a waste product of respiration

Question 3

What does the movement of gases in a plant depend on?

Answer 3

Which process (respiration or photosynthesis) is taking place more quickly

Question 4

What else (not gases) is diffused through the stomata in plants?

Answer 4

Water

Question 5

Where are the stomata found in plants?

Answer 5

At the bottom of their leaves

Question 6

Which cells in plants does photosynthesis happen in?

Answer 6

• palisade mesophyll cells

* spongy mesophyll cells

Question 7

What do the upper and lower epidermis layers do?

Answer 7

Protect the outside of the leaf

Question 8

Name the order of the layers of cells inside the plant

Answer 8

• upper epidermis layer
• palisade mesophyll layer
• spongy mesophyll layer
• lower epidermis layer

Question 9

What layer of the leaf are the plants veins found in?

Answer 9

Spongy mesophyll

Question 10

What 2 plant tissues are found in plant veins?

Answer 10

Xylem and phloem

Question 11

What does xylem do?

Answer 11

Moves water

Question 12

What does phloem do?

Answer 12

Translocation (moves sugar)

Question 13

Why is there air space in the spongy mesophyll layer?

Answer 13

To enable diffusion

Question 14

Name 2 adaptations of plant leaves that prevent water loss

Answer 14

• waxy cuticles on the outside of the leaf

* stomata and guard cells, close when there’s a short supply of water

Question 15

Name 4 adaptations of plant leaves to do with exchange of gases

Answer 15

• stomata, opens or closes to let carbon dioxide in or out
• thin and flat, good for diffusion
• root hair cells, large SA and high numbers of mitochondria for active transport
• the stomata is on the underside of the leaf because it’s cooler

Question 16

Why do water lilies have stomata on their upper surface of their leaves?

Answer 16

They’re in the sunlight so rate of transpiration is higher so their cells don’t swell up due to too much water (lysis) as it lives in water

Question 17

What is transpiration?

Answer 17

The process by which plants lose water from their leaves by evaporation

Question 18

What happens to water vapour in the plants leaves?

Answer 18

The vapour is diffused out of the stomata by osmosis

Question 19

What happens as the water leaves the plants by evaporation?

Answer 19

More water travels up through the xylem, which causes a constant flow of water in the plant

Question 20

What is the transpiration stream?

Answer 20

The cycle of water being diffused and then moving through the xylem

Question 21

How could a plant dehydrate?

Answer 21

If the rate of evaporation is greater than the water uptake from the roots

Question 22

How does temperature affect the rate of transpiration?

Answer 22

The hotter it is, the more evaporation of water in the leaves so it has to be let out of the stomata

Question 23

How does surface area affect the rate of transpiration?

Answer 23

The bigger the surface area the more transpiration because more evaporation can happen at once

Question 24

How can the concentration of water in the leaves affect the rate of transpiration?

Answer 24

The higher the concentration of water in the leaves the more diffusion due to the higher concentration gradient

Question 25

How does the humidity of the air affect the rate of transpiration?

Answer 25

The lower the humidity the more transpiration because there is a steeper concentration gradient as there is less water in the air

Question 26

How does the size and number of stomata affect the rate of transpiration?

Answer 26

The bigger or more of stomata there is the more transpiration

Question 27

How does the air flow affect the rate of transpiration?

Answer 27

Good air flow removes the water in the air so the concentration gradient is constant so there is more transpiration

Question 28

Name 3 uses of water in plants

Answer 28

• photosynthesis
• transporting nutrients and glucose
• support and structure

Question 29

Name 2 ways to measure a plants rate of transpiration

Answer 29

• potometer

* weighing it

Question 30

How can a potometer show the rate of transpiration?

Answer 30

There is an air bubble in the water so we can see how far the air bubble moves by how far it is pushed by the water moving via transpiration

Question 31

How can we use the weight of a plant in water to show its rate of transpiration?

Answer 31

The weight loss of the plant in the water shows the volume of water lost in transpiration

Question 32

Where do gases diffuse in and out of in plants?

Answer 32

Through tiny holes called stomata