1. Plant exchange and excretion

2. Packed with chloroplasts
Structure of the Leaf
Large surface area
Lots of chlorophyll
Transparent
Thin structure
Packed with chloroplasts
Network of veins
Lots of air spaces
Holes

3. Gas exchange in the leaf
The structure of the leaf allows plants to carry out gas exchange.
carbon dioxide in (daytime) : photosynthesis
Oxygen in: respiration.
Oxygen + water vapour : OUT

4. Wide spaces between ground cells – diffusion

5. The Stomata The function of the stomata is gas exchange.
Each stoma is a gap that is found in between two Guard cells.
The Guard cells control the opening and closing of the stoma.

6. The stoma and the guard cells
When water enters the guard cells they swell and have a curved shape. The gap ( the stoma) opens up between the two cells.
When water leaves the guard cells they shrink and the gap between the two cells (the stoma) closes.

8. The stoma (open) and the guard cells

9. Carbon dioxide controls the stoma
The opening and closing of the stoma depends on the levels of carbon dioxide in the plant.
When CO2 levels become low inside the plant water enters the guard cells and the stoma opens up.

10. Carbon dioxide controls the stoma
When CO2 levels are high in the plant water leaves the guard cells and they close.
This happens at night

12. Lenticels
Lenticels are small openings in the bark of a tree where gas exchange happens.

13. What about trees and woody plants ?
Lenticels often look like tiny raised blisters on a branch or twig.

14. Winter twig – showing lenticels

15. Plant excretion
Def Excretion is getting rid of waste of the metabolism from the body
Plants do not need to excrete a lot of waste:
They make their own food so they have reduced food waste to get rid of
They use most of the products of their metabolism in their bodies – i.e. oxygen is produced as a product of photosynthesis but is used for respiration.
Stomata and lenticels are the only organs of excretion.
They excrete oxygen and water vapour.