(2.40B-2.45B) Flowering Plants

Where does diffusion occur in gas exchange?

Between the atmosphere and the leaf through the stomata.

Oxygen diffuses into the plant from roots.

How does concentration gradient affect the rate of diffusion?

The steeper the gradient, the faster the rate of diffusion.

How does temperature affect the rate of diffusion?

The higher the temp, the faster the rate of diffusion.

How does particle size affect the rate of diffusion?

Smaller particles = higher rate of diffusion

How does surface area affect the rate of diffusion?

More area to diffuse = faster rate of diffusion

What is Fick’s law?

Rate of diffusion is proportional to

(SA x concentration gradient) / thickness of membrane

What is the equation for respiration?

6O2 + C6H12O6 ———> 6CO2 + 6H20 (+ATP)

How do thin leaves maximise gas exchange?

Short internal distance + thin walls = faster gas exchange

How do flat leaves maximise gas exchange?

Large SA is exposed to air so large SA:V ratio

How do many stomata maximise gas exchange?

Maintains steep conc. grad. and allows movement of gases in and out of air spaces.

How do air spaces maximise gas exchange?

Allows gas movement around loosely packed spongey mesophyll cells.

How does close contact between cells and air spaces maximise gas exchange?

Palisade cells are close to air spaces so gases used in photosynthesis can be exchanged quickly.

What is the role of stomata in gas exchange?

open when guard cells turgid, closed when guard cells flaccid.

maximise photosynthesis during the day so CO2 can diffuse in and O2 can exit.

How does photosynthesis rate change between day/night?

it can only occur when there is access to light, so doesn’t occur at night

How does respiration rate change between day/night?

It continues through both.

What happens to gas exchange in the day?

high light intensity means rate of photosynthesis > rate of respiration.

so, net diffusion of carbon dioxide into plant, and oxygen out.

What happens to gas exchange at night?

plants only respire, no photosynthesis.

net movement of oxygen into the plant and net diffusion of carbon dioxide out of the plant.

Outline the steps of an experiment to investigate effect of light intensity of net gas exchange.

• 20cm³ hydrogen-carbonate indicator into 4 tubes

• put in cotton wool

• A- no leaf, B- leaf in tube, C- leaf and cover tube in foil to block light, D- wrap in gauze for partial light

• bung each tube

• leave all 4 in light for 30 mins

What is the colour change of hydrogen bicarbonate indicator?

highest- yellow

higher- orange

atmospheric- red (compensation)

lower- magenta

lowest- purple

high to low: Your Orangutan Roasted My Papa

Hydrogen bicarbonate indicator- Yellow?

Respiration > Photosynthesis

Hydrogen bicarbonate indicator- Red?

Respiration = Photosynthesis

Hydrogen bicarbonate indicator- Purple?

Respiration < Photosynthesis