Settler

Draw a cell that has become turgid

Draw a cell that has become plasmolysed

Module 2Exchange and transport

1.2.16 Water uptake and movement up the stem

Learning Objectives Success Criteria

• Describe, the pathway by which water is transported from the root cortex to the air surrounding the leaves

• Explain the mechanism by which water is transported from the root cortex to the air surrounding the leaves.

• Define the terms root pressure, cohesion-tension theory and capillary action

(Grade D – C)

• Describe, with the aid of diagrams, the pathway by which water is transported from the root cortex to the air surrounding the leaves, with reference to the casparian strip, apoplast, symplast pathway, xylem and stomata

(Grade C –B)

• Explain the mechanism by which water is transported from the root cortex to the air surrounding the leaves, with reference to adhesion, cohesion and transpiration stream

(Grade B – A)• Explain the importance of the casparian

strip (Grade B-A)

Starter

• Name the 3 possible ways water molecules can take between cells

• Apoplast pathway• Symplast pathway• Vacuolar pathway

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The transpiration stream

Water uptake

• Write a step by step journey of how and why a water molecule would travel from the soil into the xylem

• Include keywordsMinerals, active transport, ATP, water potential

endodermis, casparian strip, cortex, water potential gradient, xylem

Casparian strip1) Blocks the apoplast pathway between cortex &

xylem2) Makes sure water & dissolved nitrate ions pass into

cytoplasm through cell membrane3) Has transporter proteins in cell membrane4) Nitrates can be actively transported from cytoplasm

of cortex into xylem, lowering the water potential so water follows by osmosis

5) Water can pass back into the cortex as apoplast pathway is blocked

Explain the importance of the casparian strip (Grade B-A)

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Transport of water up the xylemThere are 3 pathways: • 1) Root pressure• www.youtube.com/watch?v=nFL2YNgNb68• 2) Capillary action• www.youtube.com/watch?v=wOOY1szbcX4• 3) Cohesion tension• ..\..\..\..\..\..\AS Biology\UNIT 2 The variety of living

organisms\13. Exchange and transport\Unit 2 Chap 13 PowerPoints\Transport in xylem.swf

• Research your area & feedback to your group, complete sheet with 3 processes

Root pressure is caused by the mineral ions which are actively transported into xylem vessels in the root by endodermal cells. This makes the water potential of the xylem more negative and causes water to enter the xylem by osmosis.

Capillarity is responsible for some water creeping up the xylem vessels simply because they are very narrow.

Cohesion-tension theoryThe mass flow of water through the xylem

relies on 2 important properties of water:

Cohesion – the water molecules tend to stick together

Adhesion – the water molecules also tend to stick to the inside of the xylem vessels.

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How does water travel up the stem

• The mass flow of water through the xylem relies on 2 important properties of water:

• Cohesion – the water molecules tend to stick together

• Adhesion – the water molecules also tend to stick to the inside of the xylem vessels.

Cohesion-tension theoryAdd to the diagram to ensure you have understood the success criteria below

•Describe, with the aid of diagrams, the pathway by which water is transported from the root cortex to the air surrounding the leaves, with reference to the casparian strip, apoplast, symplast pathway, xylem and stomata (Grade C –B)

•Explain the mechanism by which water is transported from the root cortex to the air surrounding the leaves, with reference to adhesion, cohesion and transpiration stream (Grade B – A)

plenary

• ..\..\..\..\..\..\AS Biology\UNIT 2 The variety of living organisms\13. Exchange and transport\Unit 2 Chap 13 PowerPoints\Private life of plants - xylem, phloem.wmv

Homework

• Past exam question May 09 question 5