Transport, storage and gas exchange in flowering plants Flashcards
What does autotroph mean?
Something that can make its own food
Are plants autotrophs?
Yes, they make their own food via photosynthesis
How do roots absorb water?
Osmosis- cytoplasm of the root hairs is more concentrated than the soil water
How does water get from the root hairs to the xylem vessels?
Water diffuses from the root hairs across the ground tissue to the xylem vessels.
What does xylem do?
Forms a pipeline from the roots to the leaves.
How does water move upwards?
Root pressure and Transpiration
Describe how root pressure works.
- Water enters roots by osmosis
- Water pushes water molecule in front of it up the xylem
What is transpiration?
Loss of water vapour from the leaves and other aerial parts of the plant
Where does transpiration occur?
Occurs through the stomata.
Describe how transpiration works.
- Water evaporates from the cells in leaves- cells become turgid
- Cells are now more concentrated than xylem cells
- Water moves from xylem to ground tissue via osmosis
- Water evaporates from ground tissue into air spaces
- Air spaces= water diffuses out of stomata
- As water molecule pulled from the xylem by osmosis it “pulls” the next water molecule
- Water pulled up through the plant by transpiration
How is transpiration controlled?
- Waxy cuticle
- Stomata on underside of leaf
- Guard cells control the opening and closing of the stomata
What is the mineral calcium used for in plants?
Formation of cell walls
What is the mineral magnesium used for in plants?
Formation of chlorophyll
How are minerals absorbed into the roots?
- Active transport- requires energy
- Diffusion (does not require energy)
How are minerals transported?
In the xylem, dissolved in water
How does carbon dioxide get absorbed by the plant?
Through the stomata from the atmosphere by diffusion.
Is CO2 produced in the plant as well?
Yes, produced by leaf cells by respiration
Name two products of photosynthesis?
- Oxygen
- Glucose
What is the fate of oxygen?
- Diffuses into air spaces and out into the atmosphere
- Some used for respiration
What is the fate of glucose?
- Used for respiration
- Converted into and stored as starch
- Converted into sucrose
- Sucrose enters the phloem sieve tube cells and is transported to all parts of the plant
What is the cohesion-tension model?
Explains how water is transported to great heights against the force of gravity
Who put forward the idea for the cohesion-tension model?
Dixon and Joly- Two irish scientists
What is cohesion?
Is the sticking of similar molecules to each other
Does water have a high cohesion?
Yes
What is adhesion?
Occurs when different molecules stick together
What does water adhere to?
The wall of the xylem
Describe step 1 of cohesion -tension model
Water vapour is lost from the surface of the leaf by transpiration.
Describe step 2.
As transpiration pulls each molecule out of the xylem, the next water molecule is pulled with it due to cohesion. This creates tension in the xylem
Describe step 3.
This tension is transmitted down to the root system
Describe step 4.
The tension pulls a column of water of very small diameter up to great heights in the xylem vessels
Describe step 5.
Tension in the water columns causes the xylem (and stems) to become narrow during transpiration. To stop the xylem from collapsing inwards, each xylem cell is strengthened with lignin. When transpiration stops the xylem vessels return to their normal shape.
When are stomata closed and open?
- Open during the day
- Closed during the night
What can cause the stomata to open?
- High levels of water
- Low levels of CO2
What can cause the stomata to close?
- High CO2 levels
- Windy conditions
