Adaptations for gas exchange in plants

Question 1

Describe the function of the cuticle

Answer 1

• a waxy transparent layer
• allow light to pass through to the photosyntheitic palisade mesophyll below
• reduces water loss by vapoation through the top surface of the leaf

Question 2

Describe the function of the palisade mesophyll

Answer 2

• main photosynthetic layer packed with chloroplasts

Question 3

Describe the function of the upper epidermis

Answer 3

• transparent for light to easily penetrate to photosynthetic layers

Question 4

Describe the function of the vascular bundle

Answer 4

• contain xylem (carrying water from root) phloem (to carry sucrose to other parts of the plant) and bundle sheath parenchyma

Question 5

Describe the function of the stomata

Answer 5

• the stomatal pores allow the exchange of gases downn a concentration gradient
• the gases diffuse through intracellular spaces to and from the photosunthetic cells where they dissolve in the moist lining and fdiffuse into the cells
• guard cells open and close the stomata
• the openeing of the stomata during the day allows carbon dioxide to enter the air spaces and then the cells to be used in photosynthesis
• the closing of the stomata during the night reduces water loss

Question 6

Describe the function of the spongy medophyll

Answer 6

• surrounded by air spaces for easy diffusion of gases
• the mesophyll cell membranes are the site of has exchange

Question 7

How are leaves adapted for photsynthesis

Answer 7

• they have a large surface area and orientate perpendicular to the sun for maximum light absorption
• they are thin with a transpoarent cuticle and upper epidermis for light to penetrate into the leaf and also for efficient diffusion of gases from the stomata up through the gas spaces to the photosynthetic layers
• palisade cells paked with chloroplasts cells are densley stacked with long axes perpendicular to leaf surface

Question 8

Describe why the stomata are open

Answer 8

• tugid guard cells bend due to thickened inner walls
• opening stomatal pore

Question 9

Describe why stomata are closed

Answer 9

• flaccid guard cells meet in the middle closing the stomatal pore

Question 10

Describe the opening and closing of stomata for gas exchange

Answer 10

• in light chloroplasts in guard cells photosynthesis and produce ATP
• the ATP is used for active transport of the posstassium ions into guard cells
• starch is converted to malate
• malate and postassium ions lower water potential of guard cells and water is drawn in by osmosis
• uneven thickeneing of guard cell inner walls causes them to bend as they swell opening the stomatal pore
• the opposite occurs when there is no light closing the pore