3 Exchange: Gas Exchange in Plants

Question 1

How do plants obtain the gases they need?

Answer 1

• through the leaves

Question 2

What is required for respiration?

Answer 2

• oxygen

Question 3

What is required in photosynthesis?

Answer 3

• CO2

Question 4

When does respiration occur and what is its purpose?

Answer 4

• throughout day and night
• providing plant with supply of energy

Question 5

When does photosynthesis occur?

Answer 5

• can only occur during sunlight hours
• stops at night

Question 6

How do gases diffuse into the plant?

Answer 6

• stomata

Question 7

What is a dicot leaf?

Answer 7

• leaf composed of different tissues adapted fro specific things

Question 8

What is the dicot leaf adapted for?

Answer 8

• absorbing light
• obtaining CO2 by diffusion from atmosphere
• producing sugars
• export of sugars
• import of H2O and ions

Question 9

What is the function and adaptation of the waxy cuticle?

Answer 9

• function = a waxy layer, prevents water loss from leafs surface
• adaptation = is a waterproof layer so prevents excessive transpiration

Question 10

What is the function and adaptation of the upper epidermis?

Answer 10

• function = protects inner layers of plant, allows light through
• adaptation = transparent to let light pass to mesophyll

Question 11

What is the function and adaptation of the palisade mesophyll?

Answer 11

• function = main site of photosynthesis
• adaptation = tightly packed, many chloroplasts for maximum light absorption

Question 12

What is the function and adaptation for the spongy mesophyll?

Answer 12

• function = gas exchange ( CO2 in , O2 out)
• adaptations = air spaces for gas diffusion , some chloroplasts for photosynthesis

Question 13

What is the function and adaptation for the lower epidermis ?

Answer 13

• function = protection, control of gas exchange
• adaptations = contains stomata for diffusion of gases

Question 14

What is the function and adaptation of the stomata?

Answer 14

• function = allows gas exchange
• adaptations = opens and closes to regulate water loss and CO2 uptake

Question 15

What is the function and adaptation of the guard cells?

Answer 15

• function = control opening and closing of stomata
• adaptations = change shape due to water movement to open/ close stomata

Question 16

What is the function and adaptation of the xylem?

Answer 16

• function = transports water and minerals from roots
• adaptations = hollow tubes with lignin for strength and water conduction

Question 17

What is the function and adaptation of the phloem?

Answer 17

• function = transports sugars ( sucrose) from leaves to the rest of the plant
• adaptations = sieve tube elements with companion cells for active transport

Question 18

What are the adaptations of a leaf for efficient gas exchange?

Answer 18

• thin flat shape = large surface area for stomata, large number of air spaces, exposed spongy mesophyll cells
• many stomata = no cell is far from a stomata so diffusion pathway is short, allows diffusion of O2 and CO2 without toon much loss of water vapour, maintains conc gradient
• numerous interconnecting air spaces in spongy mesophyll = gases can readily come into contact with mesophyll cells , large SA of mesophyll cells and air spaces

Question 19

What is the structure of the guard cells when there is a lack of water?

Answer 19

• guard cells are flaccid
• stoma is closed

Question 20

What is the structure of the guard cell?

Answer 20

• thin outer wall
• thin inelastic inner wall = fundamental for the movement

Question 21

What is the structure of the guard cells when there is plenty of water?

Answer 21

• guard cells are turgid
• stoma is open
• turgid cells filled with water balloon outwards drawing the thick inner wall with them