plant gas exchange

Question 1

outline the structure/function of the palisade mesophyll

Answer 1

• main photosynthetic tissue

- cells full of chloroplasts which are arranged to ensure maximum light absorption

Question 2

outline the structure/function of the upper epidermis

Answer 2

• single cell layer
• transparent
• not many stomata

Question 3

outline the structure/function of the lower epidermis

Answer 3

• no waxy cuticle

- many stomata which allow for water loss and gas exchange

Question 4

outline the structure/function of the spongy mesophyll

Answer 4

• few chloroplasts
• loosely packed cells with large air spaces
• moist for gas exchange
• large surface area

Question 5

outline how the features of an angiosperm leaf are significant for gas exchange

Answer 5

• large surface area so more stomata for diffusion
• thin
• air spaces for diffusion between stomata and cells
• stomata allow gas exchange

Question 6

outline how the features of an angiosperm leaf are significant for photosynthesis

Answer 6

• large surface area to capture maximum light energy
• thin so light can penetrate leaf
• transparent
• lots of palisade cells to fit many mitochondria
• air spaces for diffusion of carbon dioxide
• stomata to allow carbon dioxide in

Question 7

outline the process of stomatal opening

Answer 7

• chloroplasts photosynthesise to produce ATP
• potassium ions actively transported into guard cells
• starch converted into malate
• potassium and malate lower the water potential
• guard cells expand and inner cell wall stretches

Question 8

outline the process of stomatal closing

Answer 8

• potassium ions diffuse out of guard cells
• water moves out of guard cells via osmosis
• guard cells become plasmolysed
• stomata closes

Question 9

what is meant by a mesophyte

Answer 9

plant living conditions have a good water supply

Question 10

state the stomatal distribution of a mesophyte

Answer 10

• very few on adaxial surface

- lots on abaxial surface

Question 11

state the cuticle distribution of a mesophyte

Answer 11

• waxy cuticle on adaxial surface

- very little cuticle on abaxial surface

Question 12

state 4 anatomical modifications of mesophytes

Answer 12

• air spaces present
• few hairs
• few rolled leaves
• no sclerenchyma fibres

Question 13

what is meant by a xerophyte

Answer 13

plants that live in conditions with little water

Question 14

state the stomatal distribution of a xerophyte

Answer 14

• many sunken stomata on adaxial surface

- few stomata on abaxial surface

Question 15

state the cuticle distribution of xerophytes

Answer 15

• thin cuticle on rolled leaves

- thick cuticle on flat leaves

Question 16

state 4 anatomical modifications of xerophytes

Answer 16

• air spaces present
• hairs present
• rolled leaves to trap moist air
• sclerenchyma fibres

Question 17

what is meant by a hydrophyte

Answer 17

plants that grow submerged in water

Question 18

state the stomatal distribution of hydrophytes

Answer 18

• stomata on adaxial surface

- very few stomata on abaxial surface

Question 19

state the cuticle distribution of hydrophytes

Answer 19

• little cuticle on adaxial surface

- no cuticle on adaxial surface as no need to prevent water loss

Question 20

state one anatomical modification of hydrophytes

Answer 20

large air spaces for buoyancy

Question 21

outline the method used to make a replica of the epidermis

Answer 21

• place leaf on white tile with lower epidermis face up
• apply colourless nail vanish and allow to dry
• stick sellotape on leaf and peel away, producing replica of lower epidermis
• stick tape directly on microscope slide