B2.4-6 Flashcards
What are the two transport systems in a plant?
The xylem and the phloem
What does the xylem do?
It transports water and mineral ions from the roots to the stem, leaves and flowers
What does the phloem do?
It transports dissolved sugars produced during photosynthesis and other food molecules from the leaves to all other areas of the plant
What does the vascular bundle do?
It is used for transport and provide support
What are features of the xylem vessels?
They are made from dead xylem cells
There are no cell walls at the end of the cells
The cell walls are impermeable
One way only
They have thick walls thickened with lignin
What is the structure of the phloem vessel?
It is made of living cells?
The cell walls do not completely break down instead sieve plates are formed.
Two way flow
Where are vascular bundles found?
In the leaf
In the stem
In the root
What is transpiration
The loss of water from a plants leaves
Define the transpiration stream
The constant flow of water from the roots through the xylem and out of the leaves
Describe what happens in the transpiration stream
- Water is lost from the leaves by evaporation through open stomata
- Water moves up through the stem and into the leaves to replace water lost by evaporation
- Water moves into the roots roots from the soil by osmosis. It replaces the water constantly moving up the stem
- Water moves up from the roots to the stem
How does water enter the xylem
Before the water can enter the xylem vessel it must travel from cell to cell until it reaches the center of the root.
How is water lost from the leaves
While the stomata are open, water evaporates from cells inside the leaf into the leafs air spaces. this creates a concentration gradient between the air inside the leaf and the surrounding air. Water vapour then diffuses out of the leaf into the air.
Why do plants wilt?
If a plant loses water faster than it can take in it will wilt
What happens when a plant wilts.
The leaves collapse and droop, reducing the surface area available for evaporation.
The stomata close, preventing further water loss and preventing photosynthesis.
