Plant gas exchange

Question 1

Describe how stomata open

Answer 1

1. In light chloroplasts in guard cells photosynthesise to produce ATP
2. ATP is used for active transport of k+ ions into guard cells
3. starch is converted to malate
4. malate and k+ ions lower the water potential of the cell and water is drawn in by osmosis.
5. Guard cell walls are thicker on the inner wall so bends away as they swell, opening the stomatal pore.

Question 2

How are leaves adapted for photosynthesis

Answer 2

1. Have a large surface area and orientate towards the sun for max sunlight absorption.
2. Thin with a transparent cuticle and upper epidermis for light to penetrate into the leaf.
3. Palisade cells are packed with chloroplasts.

Question 3

How is the cuticle adapted?

Answer 3

Waxy transparent layer - allowing light to pass through to palisade layer. Also reduces water lost through evaporation.

Question 4

How is the upper epidermis adpated?

Answer 4

Transparent for light to easily penetrate to the photosynthetic layers

Question 5

How is the palisde mesophyll adpated?

Answer 5

Layer is packed with chloroplasts, which can move to recieve optimum sunlight. Cells are elongated allowing light to refract down the length of the cell.

Question 6

How is the spongy mesophyll adpated

Answer 6

Lots of air spaces for diffusion of gases.