6.4: Gas exchange in the leaf of a plant

Question 1

Upper epidermis

Answer 1

The upper epidermis is a protection layer from any kind of damage

Question 2

The upper epidermis is a protection layer from any kind of damage. What does the upper epidermis do?

Answer 2

The upper epidermis protects the internal tissues from:

1. Mechanical damage
2. Bacterial and fungal invasion

Question 3

Cuticle

Answer 3

The cuticle is a waxy layer that prevents water loss from the leaf surface

Question 4

What does the palisade mesophyll layer contain?

Answer 4

The palisade mesophyll layer contains many chloroplasts

Question 5

The palisade mesophyll layer contains many chloroplasts.

Describe the palisade mesophyll cells

Answer 5

The palisade mesophyll cells are columnar cells that are closely packed together to absorb light more efficiently

Question 6

What allows gases to move in and out of the leaf?

Answer 6

The spongy mesophyll layer allows gases to move:

1. In
2. Out of

the leaf

Question 7

Spongy mesophyll layer

Answer 7

The spongy mesophyll layer is irregular cells loosely packed together to leave numerous large air spaces to allow rapid diffusion of gases throughout the leaf

Question 8

Lower epidermis

Answer 8

The lower epidermis is the same as the upper epidermis, except the cuticle is thinner

Question 9

The lower epidermis is the same as the upper epidermis, except the cuticle is thinner.

Why is the cuticle thinner?

Answer 9

The cuticle is thinner, because it’s on the bottom of the leaf

Question 10

The lower epidermis is the same as the upper epidermis, except the cuticle is thinner.

The cuticle is thinner, because it’s on the bottom of the leaf and therefore it is what?

Answer 10

The cuticle is thinner, because it’s on the bottom of the leaf and therefore it is less exposed to the Sun

Question 11

The lower epidermis is the same as the upper epidermis, except the cuticle is thinner.

The cuticle is thinner, because it’s on the bottom of the leaf and therefore it is less exposed to the Sun, so what?

Answer 11

The cuticle is thinner, because it’s on the bottom of the leaf and therefore it is less exposed to the Sun, so there will be less evaporation

Question 12

Stomata

Answer 12

The stomata are an opening that allows gases to pass through it to go:

1. Into

Or,

2. Out of the leaf

Question 13

The stomata are an opening that allows gases to pass through it to go into or out of the leaf.

What do stomata also do?

Answer 13

Stomata also let water out during respiration

Question 14

The stomata are an opening that allows gases to pass through it to go into or out of the leaf.

Stomata also let water out during respiration.

What is this process called?

Answer 14

This process is called transpiration

Question 15

What is the vascular bundle (vein) made up of?

Answer 15

The vascular bundle (vein) is made up of:

1. Xylem
2. Phloem

Question 16

What is the function of xylem?

Answer 16

The function of xylem is to transport:

1. Water
2. Mineral salts

towards the leaf

Question 17

What is the function of phloem?

Answer 17

The function of phloem is to transport organic substances away from the leaf

Question 18

The function of phloem is to transport organic substances away from the leaf.

What does phloem generally transport?

Answer 18

Phloem generally transports sucrose

Question 19

What do guard cells do?

Answer 19

Guard cells control the:

1. Opening
2. Closing

of the stomata

Question 20

What do guard cells have?

Answer 20

Guard cells have a:

1. Thin outer wall
2. Thick, inelastic inner wall

Question 21

Guard cells have a thin outer wall and a thick, inelastic inner wall.

What is the thick, inelastic inner wall fundamental for?

Answer 21

The thick, inelastic inner wall is fundamental for movement

Question 22

When the guard cells are flaccid (lack of water), what are the stoma?

Answer 22

When the guard cells are flaccid (lack of water), the stoma are closed

Question 23

When the guard cells are turgid (plenty of water), what are the stoma?

Answer 23

When the guard cells are turgid (plenty of water), the stoma are open

Question 24

When the guard cells are turgid (plenty of water), the stoma are open, why?

Answer 24

When the guard cells are turgid (plenty of water), the stoma are open, because the inside thick, inelastic wall doesn’t open as much as it should

Question 25

When the guard cells are turgid (plenty of water), the stoma are open, because the inside thick, inelastic wall doesn't open as much as it should, so what is there?

Answer 25

When the guard cells are turgid (plenty of water), the stoma are open, because the inside thick, inelastic wall doesn't open as much as it should, so there is a hole

Question 26

How many parts does photosynthesis have?

Answer 26

Photosynthesis has 2 parts, a: 1. Light-dependent part 2. Light-independent part

Question 27

Stomatal opening over 24 hours: When do the stomata begin to open?

Answer 27

The stomata begin to open at dawn

Question 28

Stomatal opening over 24 hours: The stomata begin to open at dawn. What does the increased light intensity cause?

Answer 28

The increased light intensity causes more stomata to open

Question 29

Stomatal opening over 24 hours: The stomata begin to open at dawn. The increased light intensity causes more stomata to open. When do some plants close stomata?

Answer 29

Some plants close stomata during the hottest weather

Question 30

Stomatal opening over 24 hours: The stomata begin to open at dawn. The increased light intensity causes more stomata to open. Some plants close stomata during the hottest weather. This is an adaptation for what environments?

Answer 30

This is an adaptation for hot, dry environments

Question 31

Stomatal opening over 24 hours: The stomata begin to open at dawn. The increased light intensity causes more stomata to open. Some plants close stomata during the hottest weather. This is an adaptation for hot, dry environments. When do stomata close?

Answer 31

Stomata close as the sun sets

Question 32

Stomata are closed when there isn't much what in the guard cells?

Answer 32

Stomata are closed when there isn't much water in the guard cells

Question 33

Stomata are closed when there isn't much water in the guard cells. How does water get inside the guard cells?

Answer 33

Water gets inside the guard cells by osmosis

Question 34

Stomata are closed when there isn't much water in the guard cells. Water gets inside the guard cells by osmosis. The guard cells become what and, because of what, they do what?

Answer 34

The guard cells: 1. Become turgid 2. Because of their thick, inelastic inner wall, they curve and open the stomata

Question 35

Stomata are closed when there isn't much water in the guard cells. Water gets inside the guard cells by osmosis. The guard cells become turgid and ,because of their thick, inelastic inner wall, they curve and open the stomata. What is this process influenced by?

Answer 35

This process is influenced by: 1. Water availability 2. Carbon dioxide concentration 3. Light intensity

Question 36

What does the mesophyll layer consist of?

Answer 36

The mesophyll layer consists of 2 parts, the: 1. Palisade mesophyll layer 2. Spongy mesophyll layer

Question 37

When photosynthesis is not occurring, in the dark, for example, why does oxygen diffuse into the leaf?

Answer 37

When photosynthesis is not occurring, in the dark, for example, oxygen diffuses into the leaf, because it is constantly being used by cells during respiration

Question 38

When photosynthesis is not occurring, in the dark, for example, oxygen diffuses into the leaf, because it is constantly being used by cells during respiration. In the same way, carbon dioxide produced when does what?

Answer 38

In the same way, carbon dioxide produced during respiration diffuses out of the leaf

Question 39

How are the diffusion gradients in and out of the leaf maintained?

Answer 39

The diffusion gradients in and out of the leaf are maintained by: 1. Mitochondria carrying out respiration 2. Chloroplasts carrying out photosynthesis

Question 40

The structure of a plant leaf and gas exchange: In some ways, gas exchange in plants is similar to that of insects, how?

Answer 40

In some ways, gas exchange in plants is similar to that of insects: 1. No living cell is far from the external air and therefore a source of oxygen and carbon dioxide 2. Diffusion takes place in the gas phase (air)

Question 41

The structure of a plant leaf and gas exchange: In some ways, gas exchange in plants is similar to that of insects - No living cell is far from the external air and therefore a source of oxygen and carbon dioxide and diffusion takes place in the gas phase (air), which does what?

Answer 41

In some ways, gas exchange in plants is similar to that of insects: 1. No living cell is far from the external air and therefore a source of oxygen and carbon dioxide 2. Diffusion takes place in the gas phase (air), which makes it more rapid than if it were in water

Question 42

The structure of a plant leaf and gas exchange: In some ways, gas exchange in plants is similar to that of insects - No living cell is far from the external air and therefore from a source of oxygen and carbon dioxide and diffusion takes place in the gas phase (air), which makes it more rapid than if it were in water. Overall, therefore, there is a short, fast diffusion pathway. In addition, what do the air spaces inside a leaf have compared with what?

Answer 42

In addition, the air spaces inside a leaf have a very large surface area compared with the volume of living tissue

Question 43

The structure of a plant leaf and gas exchange: In some ways, gas exchange in plants is similar to that of insects - No living cell is far from the external air and therefore from a source of oxygen and carbon dioxide and diffusion takes place in the gas phase (air), which makes it more rapid than if it were in water. Overall, therefore, there is a short, fast diffusion pathway. In addition, the air spaces inside a leaf have a very large surface area compared with the volume of living tissue. There is no specific transport system for gases, which simply move in and through the plant by diffusion. Most gaseous exchange occurs in the leaves, which show the following adaptations for rapid diffusion: 1. Many small pores, called stomata, and so no cell is far from what and therefore what is short?

Answer 43

Many small pores, called stomata, and so no cell is far from a stoma and therefore the diffusion pathway is short

Question 44

The structure of a plant leaf and gas exchange: In some ways, gas exchange in plants is similar to that of insects - No living cell is far from the external air and therefore from a source of oxygen and carbon dioxide and diffusion takes place in the gas phase (air), which makes it more rapid than if it were in water. Overall, therefore, there is a short, fast diffusion pathway. In addition, the air spaces inside a leaf have a very large surface area compared with the volume of living tissue. There is no specific transport system for gases, which simply move in and through the plant by diffusion. Most gaseous exchange occurs in the leaves, which show the following adaptations for rapid diffusion: 1. Many small pores, called stomata, and so no cell is far from a stoma and therefore the diffusion pathway is short. 2. Numerous what that occur throughout the mesophyll layer?

Answer 44

Numerous interconnecting air spaces that occur throughout the mesophyll layer

Question 45

The structure of a plant leaf and gas exchange: In some ways, gas exchange in plants is similar to that of insects - No living cell is far from the external air and therefore from a source of oxygen and carbon dioxide and diffusion takes place in the gas phase (air), which makes it more rapid than if it were in water. Overall, therefore, there is a short, fast diffusion pathway. In addition, the air spaces inside a leaf have a very large surface area compared with the volume of living tissue. There is no specific transport system for gases, which simply move in and through the plant by diffusion. Most gaseous exchange occurs in the leaves, which show the following adaptations for rapid diffusion: 1. Many small pores, called stomata, and so no cell is far from a stoma and therefore the diffusion pathway is short. 2. Numerous interconnecting air spaces that occur throughout the mesophyll layer, why?

Answer 45

Numerous interconnecting air spaces that occur throughout the mesophyll layer, so that gases can readily come into contact with the mesophyll cells

Question 46

The structure of a plant leaf and gas exchange: In some ways, gas exchange in plants is similar to that of insects - No living cell is far from the external air and therefore from a source of oxygen and carbon dioxide and diffusion takes place in the gas phase (air), which makes it more rapid than if it were in water. Overall, therefore, there is a short, fast diffusion pathway. In addition, the air spaces inside a leaf have a very large surface area compared with the volume of living tissue. There is no specific transport system for gases, which simply move in and through the plant by diffusion. Most gaseous exchange occurs in the leaves, which show the following adaptations for rapid diffusion: 1. Many small pores, called stomata, and so no cell is far from a stoma and therefore the diffusion pathway is short. 2. Numerous interconnecting air spaces that occur throughout the mesophyll layer, so that gases can readily come into contact with the mesophyll cells. 3. What of mesophyll cells for rapid diffusion?

Answer 46

A large surface area of mesophyll cells for rapid diffusion

Question 47

Stomata are minute pores that occur where?

Answer 47

Stomata are minute pores that occur: 1. Mainly ,but 2. Not exclusively ,on the leaves

Question 48

Stomata are minute pores that occur mainly, but not exclusively, on the leaves, especially the what?

Answer 48

Stomata are minute pores that occur: 1. Mainly ,but 2. Not exclusively ,on the leaves, especially the underside

Question 49

Stomata are minute pores that occur mainly, but not exclusively, on the leaves, especially the underside. What is each stoma (singular) surrounded by?

Answer 49

Each stoma (singular) is surrounded by a pair of special cells, guard cells

Question 50

Stomata are minute pores that occur mainly, but not exclusively, on the leaves, especially the underside. Each stoma (singular) is surrounded by a pair of special cells, guard cells. What can these guard cells open and close?

Answer 50

These guard cells can: 1. Open 2. Close the stomatal pore

Question 51

Stomata are minute pores that occur mainly, but not exclusively, on the leaves, especially the underside. Each stoma (singular) is surrounded by a pair of special cells, guard cells. These guard cells can open and close the stomatal pore. In this way, they can control the rate of gaseous exchange. Why is this important?

Answer 51

This is important, because terrestrial organisms lose water by evaporation

Question 52

Stomata are minute pores that occur mainly, but not exclusively, on the leaves, especially the underside. Each stoma (singular) is surrounded by a pair of special cells, guard cells. These guard cells can open and close the stomatal pore. In this way, they can control the rate of gaseous exchange. This is important, because terrestrial organisms lose water by evaporation. Plants have evolved to balance the conflicting needs of gas exchange and control of water loss by closing stomata at times when water loss would be what?

Answer 52

Plants have evolved to balance the conflicting needs of: 1. Gas exchange 2. Control of water loss by closing stomata at times when water loss would be excessive