Plant Systems - Gas Exchange & Transport System (PPT 7-10) [U1/ T2]

Question 1

What is the structure of leaves?

Answer 1

• Broad and held out by petiole
• Have stomata (holes)
• Have veins
• Packed with chloroplasts, and therefore chlorophyll
• Are thin
• Waxy outer layer called cuticle

Question 2

What is their function pertaining to photosynthesis?

- Broad and held out by petiole

Answer 2

• Maximise light exposure

- Minimise water loss

Question 3

What is their function pertaining to photosynthesis?

- Have stomata (holes)

Answer 3

Allow carbon dioxide in and oxygen out

Question 4

What is their function pertaining to photosynthesis?

- Have veins

Answer 4

Transport the reactants and products of photosynthesis.

Question 5

What is their function pertaining to photosynthesis?

- Packed with chloroplasts, and therefore chlorophyll

Answer 5

Contain a light trapping pigment

Question 6

What is their function pertaining to photosynthesis?

- Are thin

Answer 6

• Light penetrates to all photosynthetic cells

- Short diffusion distance

Question 7

What is their function pertaining to photosynthesis?

- Waxy outer layer called cuticle

Answer 7

Limit water loss from inside the leaf

Question 8

What is the tissue type, structure, and function of the upper and lower epidermis?

Answer 8

T: Dermal

S: Single transparent layer of cells.

F: Protect the leaf but allow light to pass through.

Question 9

What is the tissue type, structure, and function of the palisade mesophyll?

Answer 9

T: Ground

S: Consists of closely packed cells

F: Site of photosynthesis as its where the chloroplasts are located.

Question 10

What is the tissue type, structure, and function of the spongy mesphyll?

Answer 10

T: Ground

S: Loosely packed layer of more rounded cells.
- Large air spaces

F: Facilitate water and gas transport required for photosynthesis.

Question 11

What is the tissue type, structure, and function of the xylem?

Answer 11

T: Vascular

S: Series of hollow pipes that are heavily stregnthed.

F: Carrying water and dissolved mineral ions.

Question 12

What is the tissue type, structure, and function of the phloem?

Answer 12

T: Vascular

S: Comprised of sieve tubes and companion cells.

F: Carry organic solutions (sugars).

Question 13

What is the tissue type, structure, and function of the stomata (guard cells)?

Answer 13

T: Meristematic

S: Is lined by two guard cells.

F: Control its aperture.

Question 14

State 3 ways in which leaves are structured to facilitate gas exchange?

Answer 14

1) Flat leaf shape increases surface area for diffusion
2) Internal air spaces allow gases to reach cells
3) Guard cells control the opening and closing of stroma to to regulate water loss.

Question 15

Answer the following questions about the xylem vessel

1) Structure
2) Alive or dead
3) Presence of lignin?
4) Substance transported?
5) Transport direction?
6) Source of energy for transport

Answer 15

1) Long water filled tube made from dead lignifed mature cells joined end to end.
2) Dead
3) Yes
4) Water and minerals
5) Upwards
6) Passive

Question 16

Answer the following questions about the tracheid’s

1) Structure
2) Alive or dead
3) Presence of lignin?
4) Substance transported?
5) Transport direction?
6) Source of energy for transport

Answer 16

1) Single large tapering water filled lignified cells that have many pits in their side walls.
2) Dead
3) Yes
4) Water
5) Side wall pits
6) Passive

Question 17

Answer the following questions about the sieve tubes

1) Structure
2) Alive or dead
3) Presence of lignin?
4) Substance transported?
5) Transport direction?
6) Source of energy for transport

Answer 17

1) Linear rows of thin walled elongated cells with their cell ends perforated by holes to form sieve plates.
2) Alive
3) No
4) Sugar
5) Upwards and downwards
6) Active

Question 18

Answer the following questions about companion cells

1) Structure
2) Alive or dead
3) Presence of lignin?
4) Substance transported?
5) Transport direction?
6) Source of energy for transport

Answer 18

1) Thin walled nucleated cell adjacent to sieve tubes.
2) Alive
3) No
4) Support only
5)
6) Active

Question 19

What are the tell tale signs to identify the phloem from the xylem - consider the position and size and staining.
Indicate how you can recognise the sieve tubes from companion cells?

Answer 19

• The dark cells are companion cells.
• The largest cells are sieve tube members.
• Xylem are the largest diameter tubes.
• Phloem is usually stained different due to lack of lignification.

Question 20

What are the 2 methods of water movement?

Answer 20

1) Pass along cell walls like water travelling along blotting paper.
- Not a selective method.
- Is reversible
- Does not involve a concentration gradient
- Called extra cellular

2) Cytoplasmic route
- Water and dissolved minerals pass through the cell membrane into each cells cytoplasm towards the xylem.
- Involves movement via gradients

Question 21

Explain the movement of water from the root hair cell to the xylem tissue.

Answer 21

• The 1st pathway is when it travels along the cell wall.
• The 2nd pathway is the cytoplasmic route, they pass through the cell membrane.
• The Casparian strip is a waxy outer layer of cells which acts as a safety net for a plant.