Gas Exchange In Plants

Question 1

What gases do plants exchange?

Answer 1

Oxygen, carbon dioxide and water vapour.

Question 2

What adaptions do plants have for efficient diffusion?

Answer 2

-Leaf tissue is a few cells thick so has a short diffusion pathway.
-Have stomata to maintain a steep concentration gradient.
-Mesophyll cells have a large surface area.

Question 3

What theory can explain tanspiration?

Answer 3

The cohesion tension theory.

Question 4

What water property allows transpiration to happen?

Answer 4

Cohesion between molocules

Question 5

What is the process of transpiration?

Answer 5

-Water vapour diffuses out through the stomata down a diffusion gradient.
-Water evaporates from surfaces on cells lining the substomatal cavity.
-Water moves across the leaf down a water potential gradient.
-Water leaving the xylem creates tension.
-Water moves up the xylem due to cohesion and the continues chain creates tension to form a transpiration stream.
-Water potential is roots is changed so water moves in by osmosis.

Question 6

When turgid what do guard cells do?

Answer 6

Curve apart.

Question 7

When flaccid what do guard cells do?

Answer 7

Edges of the cells close together.

Question 8

How do plants reduce water loss?

Answer 8

-Have a waxy cuticle which is impermeable to water.
-Stomata are under leaves so it is cooler.
-Thick leaves to reduce water loss.
-Stomata close during certain points of the day.
-Stomata can be found sunken and in pits.