Water Movement through a Plant Flashcards
What happens once water has entered the root hair cells by osmosis?
It moves through the roots, up the xylem and into the leaves down a Ψ gradient
What maintains the Ψ gradient?
Constant evaporation of water from leaves
What is the transpiration stream?
The movement of water through a plant
How does water travel through the roots?
Two pathways:
-Symplast
-Apoplast
How does water enter these pathways?
By osmosis
What is the first step of water movement in the roots?
In the symplast pathways where water moves through living parts (cytoplasm) of the cell by osmosis
What connects the cytoplasm of adjacent cells?
Plasmodesmata
What is the second step of water movement in the roots?
In the apoplast pathway where water moves through the non-living parts of the cell (spaces in cell wall) down a pressure gradient
What is this movement an example of?
Mass Flow
What can water in the apoplast pathway carry?
Solutes
What is the third step of water movement in the roots?
When water in the apoplast pathway reaches the endodermis, the water’s path is blocked by the casparian strips
What is the fourth step of water movement in the roots?
This block forces water to enter the symplast pathway
Why is it useful that the water enters the symplast pathway?
Helps to protect the plant
How and why does it help to protect the plant?
As the water had to pass through a partially permeable membrane via osmosis to get into the cytoplasm MEANING that large of harmful solutes in apoplast cant’ get through
What is the fifth step of water movement through the roots?
Once past the casparian strip, mineral ions in cytoplasm of endodermal cells are actively transported into the cytoplasm of the cells surrounding the xylem
What is the sixth step of water movement through the roots?
The active transport in step 5 generates a higher Ψ in the cytoplasm of the endoermal cells than the ones surrounding the xylem so water follows
What is the seventh and final step of water movement through the roots?
Once inside vascular bundle, the mineral ions are actively transported into apoplast so water follows by osmosis then entering the xylem
What does this movement in step 7 create?
High root pressure at the bottom of the xylem which helps water to start moving up
How does water move from roots the leaves?
Due to:
-Cohesion
-Tension
-Adhesion
What is cohesion, tension and adhesion?
C-sticking together
T-pulling force
A-sticking to something else
What does cohesion and tension help to do?
Move water up the xylem against gravity
What is this movement against gravity called?
Cohesion-Tension theory
What is the first step of the cohesion tension theory?
Water evaporated from the leaves at the top of the xylem
What is the second step of the cohesion tension theory?
Tension is created (like a suction) which pulls more water into the leaves
