3.4the breathing system and excretion plant exchange and excretion
TRANSCRIPT
3.4The breathing system and excretion
Plant exchange and excretion
3.4The breathing system and excretion
Large surface area
Thin structure
Network of veins
Lots of chlorophyll
Structure of the Leaf
Transparent
Packed with chloroplasts
Lots of air spaces
Holes
3.4The breathing system and excretion
Gas exchange in the leafThe structure of the leaf allows plants to carry out gas
exchange.
carbon dioxide in (daytime) : photosynthesis
Oxygen in: respiration.
Oxygen + water vapour : OUT
3.4The breathing system and excretionWide spaces between ground cells – diffusion
3.4The breathing system and excretion
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.
3.4The breathing system and excretion
When water leaves the guard cells they shrink and the gap between the two cells (the stoma) closes.
When water enters the guard cells they swell and have a curved shape. The gap ( the stoma) opens up between the two cells.
The stoma and the guard cells
3.4The breathing system and excretion
3.4The breathing system and excretion
The stoma (open) and the guard cells
3.4The breathing system and excretion
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.
3.4The breathing system and excretion
Carbon dioxide controls the stoma• When CO2 levels are high in the plant water leaves the
guard cells and they close.
3.4The breathing system and excretion
3.4The breathing system and excretion
Lenticels• Lenticels are small openings in the bark of a tree
where gas exchange happens.
3.4The breathing system and excretionWhat about trees and woody plants ?
Lenticels often look like tiny raised blisters on a branch or twig.
3.4The breathing system and excretionWinter twig – showing lenticels
3.4The breathing system and excretion
Plant excretionDef 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.