Plant Gas Exchange

Question 1

1. What Movement do plants entirely rely on for exchange of gases?
2. What 3 characteristics help increase the rate?

Answer 1

1. Diffusion.
2. Thin, Large Surface Area , permeated by air spaces.

Question 2

1. What is the order (highest to lowest) of the parts of the leaf?
2. What is contained in a vascular bundle and what is the outermost layer called?

Answer 2

1. Cuticle, Upper Epidermis, Palisade Mesophyll, Spongy Mesophyll, Lower Epidermis.
2. Xylem and Phloem, Sheath Parenchyma.

Question 3

What does the cuticle and upper epidermis ‘s role in a leaf?

Answer 3

Allows light to enter through to Palisade Mesophyll to help with Photosynthesis.

Question 4

1. What are 2 characteristics of Palisade Cells?
   2.. What is the role of them?

Answer 4

1. They’re Elongated and packed full of moving Chloroplasts.
2. They maximise light absoprtion for photosynthesis.

Question 5

How does having a large surface area and being thin help a leaf?

Answer 5

Large SA- Allow for a large number of Stomata and to Capture maximum light energy.
Thin- Allows short diffusion pathway for gases and light to penetrate throught the leaf.

Question 6

1. Can light pass through to the Spongy Mesophyll?
2. What do the spaces in the mesophyll cells allow?
3. What characterstic allows the gases to dissolve?

Answer 6

1. Yes
2. Allow CO2 to diffuse into the cells and O2 to diffuse away.
3. It being moist.

Question 7

What does the cuticle prevent?

Answer 7

Prevents Water Loss which also reduces Gas Exchange.

Question 8

Describe the Process of Stoma opening.
(Stoma closing is the opposite of all this).

Answer 8

1. Potassium ions are actively transported into the guard cells.
2. Starch (insoluble) is converted into malate (soluble).
3. The combination of these lowers the water potential into the guard cells.
4. Water moves into the guard cells down a water potential gradient.
5. The cell becomes turgid.
6. The cells curve due to uneven cuticular thickening- inner wall is less elastic than the outer.

Question 9

Why do Stoma open and close?
What is the definition of this word?

Answer 9

Turgor- The internal Water Pressure inside the guard cells.

Question 10

How do Stoma allow K+ ions to be actively transported into the guard cells?

Answer 10

The chloroplasts in the guard cells produce ATP through Photosynthesis.

Question 11

How does the opening and closing of stomatal pores alter water loss?

Answer 11

It’s altered by transpiration- water leaves through a plant by evaporation.

Question 12

What types of plants are classified based on their water supply structure?

Answer 12

Hydrophytes, mesophytes, xerophytes

This classification is based on the plant’s adaptations to different water availability conditions.

Question 13

What is a characteristic of hydrophytes?

Answer 13

Roots submerged in water with floating leaves

Hydrophytes have little need for support or transport tissues due to their aquatic environment. They also have little or no cuticle and stomata only on the upper surface of the leaves. Large air spaces.

Question 14

What adaptations do xerophytes have for water conservation?

Answer 14

Modified structures to prevent excessive water loss

Examples include thick cuticles, sunken stomata, and specialized leaf shapes.

Question 15

What are characteristics of mesophytes?

Answer 15

Plants of temperate regions and flourish in habitats with adequate water supply.

They need to survive unfavourable times by shedding their leaves, surviving underground or as dormant seeds.