Uptake Of Water And Mineral Salts By The Plant Flashcards
What needs to happen for the uptake of water to occur?
There needs to be a high ψ in the soil and a low ψ in the leaf
What are the three forces that work to move water upward?
Capillary action
Root pressure
Transpiration
What is the usual ψ of a root hair?
Low
What are the steps of water movement in a plant?
Into root hair
Through parenchyma cells or through the intercellular air spaces
Through the passage cells
To the xylem
Why does water need to keep moving through the xylem?
To keep a low ψ there
So osmosis will work
What is the Casparian strip?
Cork stretching between two endodermis cells
How does capillary action work?
The water molecules are attracted to the walls of the xylem (adhesion) and to each other (cohesion)
So they are forced up
How does transpiration cause water to move upward?
The leaf loses water
Its ψ decreases
The water will move up, because of osmosis
How does root pressure cause water to move upward?
The constant influx of water into the roots causes pressure to build which pushes the water up the xylem
How do the guard cells close?
The cell wall is thicker near the stoma
The turgor pressure from the vacuole causes it to bend (open)
When their is less water, the vacuole will become flaccid
The cells no longer bend
The stoma closes
What are the three steps of water absorption in plants?
Uptake of water and mineral salts by roots
Movement of water from root to xylem
Upward movement from xylem to the leaves
Why does the root hair haves low ψ?
The vacuole is full of dissolved solutes (cell sap)
How are mineral salts absorbed by the root?
Through active transport
Why is ATP needed to absorb minerals?
The minerals move against their concentration gradient
There are more solutes in the roots
Why does water move from the vacuoles of root cells into the xylem?
There is a lower ψ in the xylem
What two routes can water take in order to get to the xylem?
Through the parenchyma in the cortex
Through the intercellular air spaces of the parenchyma cells
What are passage cells?
Endodermis cells that allow water through them and into the xylem
How do the Casparian strips direct water to the xylem?
Are impermeable to water
Force the water through the passage cells
Why does capillary action work in the xylem?
Forces of adhesion and cohesion of water
The tubes have a very small bore
What is the main force that cause water to move up the stem?
Transpiration pull
What is transpiration?
The release of water vapour through the stomata of a plant leaf
What does transpiration cause?
A water potential gradient, in the direction of the root xylem, to be created
What is the transpiration stream?
The water that is pulled upwards because of the transpiration pull
How are mineral salts moved from the roots upwards?
They are dissolved the transpiration stream
