Water Movement through a Plant Flashcards

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1
Q

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

A

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

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2
Q

What maintains the Ψ gradient?

A

Constant evaporation of water from leaves

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3
Q

What is the transpiration stream?

A

The movement of water through a plant

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4
Q

How does water travel through the roots?

A

Two pathways:
-Symplast
-Apoplast

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5
Q

How does water enter these pathways?

A

By osmosis

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6
Q

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

A

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

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7
Q

What connects the cytoplasm of adjacent cells?

A

Plasmodesmata

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8
Q

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

A

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

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9
Q

What is this movement an example of?

A

Mass Flow

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10
Q

What can water in the apoplast pathway carry?

A

Solutes

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11
Q

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

A

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

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12
Q

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

A

This block forces water to enter the symplast pathway

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13
Q

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

A

Helps to protect the plant

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14
Q

How and why does it help to protect the plant?

A

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

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15
Q

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

A

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

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16
Q

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

A

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

17
Q

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

A

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

18
Q

What does this movement in step 7 create?

A

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

19
Q

How does water move from roots the leaves?

A

Due to:
-Cohesion
-Tension
-Adhesion

20
Q

What is cohesion, tension and adhesion?

A

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

21
Q

What does cohesion and tension help to do?

A

Move water up the xylem against gravity

22
Q

What is this movement against gravity called?

A

Cohesion-Tension theory

23
Q

What is the first step of the cohesion tension theory?

A

Water evaporated from the leaves at the top of the xylem

24
Q

What is the second step of the cohesion tension theory?

A

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

25
Q

What is the third step of the cohesion tension theory?

A

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

26
Q

What is the fourth step of the cohesion tension theory?

A

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

27
Q

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

A

Carbohydrates in the walls of xylem

28
Q

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

A

Adhesion and helps water move up the plant

29
Q

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

A

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

30
Q

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

A

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