Water Movement through a Plant

Question 1

What happens once water has entered the root hair cells by osmosis?

Answer 1

It moves through the roots, up the xylem and into the leaves down a Ψ gradient

Question 2

What maintains the Ψ gradient?

Answer 2

Constant evaporation of water from leaves

Question 3

What is the transpiration stream?

Answer 3

The movement of water through a plant

Question 4

How does water travel through the roots?

Answer 4

Two pathways:
-Symplast
-Apoplast

Question 5

How does water enter these pathways?

Answer 5

By osmosis

Question 6

What is the first step of water movement in the roots?

Answer 6

In the symplast pathways where water moves through living parts (cytoplasm) of the cell by osmosis

Question 7

What connects the cytoplasm of adjacent cells?

Answer 7

Plasmodesmata

Question 8

What is the second step of water movement in the roots?

Answer 8

In the apoplast pathway where water moves through the non-living parts of the cell (spaces in cell wall) down a pressure gradient

Question 9

What is this movement an example of?

Answer 9

Mass Flow

Question 10

What can water in the apoplast pathway carry?

Answer 10

Solutes

Question 11

What is the third step of water movement in the roots?

Answer 11

When water in the apoplast pathway reaches the endodermis, the water’s path is blocked by the casparian strips

Question 12

What is the fourth step of water movement in the roots?

Answer 12

This block forces water to enter the symplast pathway

Question 13

Why is it useful that the water enters the symplast pathway?

Answer 13

Helps to protect the plant

Question 14

How and why does it help to protect the plant?

Answer 14

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

Question 15

What is the fifth step of water movement through the roots?

Answer 15

Once past the casparian strip, mineral ions in cytoplasm of endodermal cells are actively transported into the cytoplasm of the cells surrounding the xylem

Question 16

What is the sixth step of water movement through the roots?

Answer 16

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

Question 17

What is the seventh and final step of water movement through the roots?

Answer 17

Once inside vascular bundle, the mineral ions are actively transported into apoplast so water follows by osmosis then entering the xylem

Question 18

What does this movement in step 7 create?

Answer 18

High root pressure at the bottom of the xylem which helps water to start moving up

Question 19

How does water move from roots the leaves?

Answer 19

Due to:
-Cohesion
-Tension
-Adhesion

Question 20

What is cohesion, tension and adhesion?

Answer 20

C-sticking together
T-pulling force
A-sticking to something else

Question 21

What does cohesion and tension help to do?

Answer 21

Move water up the xylem against gravity

Question 22

What is this movement against gravity called?

Answer 22

Cohesion-Tension theory

Question 23

What is the first step of the cohesion tension theory?

Answer 23

Water evaporated from the leaves at the top of the xylem

Question 24

What is the second step of the cohesion tension theory?

Answer 24

Tension is created (like a suction) which pulls more water into the leaves

Question 25

What is the third step of the cohesion tension theory?

Answer 25

Water molecules are cohesive so stick together-when the top ones are pulled up, the others follow

Question 26

What is the fourth step of the cohesion tension theory?

Answer 26

This lowers the water potential at the bottom of the xylem so more water enters the xylem

Question 27

As well as being attracted to eachother, what are water molecules also attracted to?

Answer 27

Carbohydrates in the walls of xylem

Question 28

What is this attraction to carbohydrates called and what does it do?

Answer 28

Adhesion and helps water move up the plant

Question 29

What is the first step as water moves through to the leaves?

Answer 29

Water leaves at the leaf and moves into the mesophyll cells mainly by the apoplast pathway

Question 30

What is the second step as water moves through to the leaves?

Answer 30

Water evaporated from the cell walls into the air spaces of the spongy mesophyll and then diffuses out of the leaf through the stomata and down a Ψ gradient