IT’S A IT’S A GREEN WORLDGREEN WORLD

WATER, WATER WATER, WATER

EVERYWHEREEVERYWHERE

How do tall trees get enough How do tall trees get enough water?water?

Redwoods are the tallest species of tree in the world.

How does a plant this size get water from its roots to the branches at the top?

The tallest redwood ever measured was 120 metres tall. That is six times the height of the Angel of the North!

The water will travel up the stem, or trunk, of the tree.

Starter

Water, water Water, water everywhereeverywhereLearning objectivesLearning objectives Describe how water Describe how water

travels through a plant.travels through a plant. Explain that Explain that

transpiration is a transpiration is a consequence of the way consequence of the way leaves are adapted for leaves are adapted for photosynthesis.photosynthesis.

Explain how the cellular Explain how the cellular structure of a leaf is structure of a leaf is adapted to reduce adapted to reduce water losswater loss

Success criteriaSuccess criteria Student should be Student should be

able to draw a plant able to draw a plant showing the direction showing the direction of flow of water.of flow of water.

Successfully complete Successfully complete a stomatal peel.a stomatal peel.

Plants and condensationPlants and condensationLook at the demonstration (WorksheetB4b7)Look at the demonstration (WorksheetB4b7)

Where has the condensation in bell jar A come from?Where has the condensation in bell jar A come from?

How do you know that it has not come from the air?How do you know that it has not come from the air?

The condensation is tested with dry cobalt chloride The condensation is tested with dry cobalt chloride paper, which is blue. Why is the cobalt chloride paper paper, which is blue. Why is the cobalt chloride paper dried?dried?

When the dry cobalt chloride paper is put against the When the dry cobalt chloride paper is put against the condensation, what colour does it become?condensation, what colour does it become?

What does this prove?What does this prove?

Movement of water up a stem

What is transpiration?What is transpiration?

Although it may seem bad for plants, transpiration actually moves water from the roots to the top of the plant, without using energy.

How does this work?

Transpiration is the loss of water by evaporation from plants.

Transpiration

Draw a diagram of a tree showing the process of transpiration – use the textbook fig8 p60 to help you.

TranspirationTranspiration

Evaporation of water from a leaf creates a Evaporation of water from a leaf creates a suction effect. This pulls the water up suction effect. This pulls the water up through the stem. This movement of water through the stem. This movement of water is useful because:is useful because:

Evaporation of water cools the plantEvaporation of water cools the plant

Photosynthesis needs a supply of waterPhotosynthesis needs a supply of water

A cell full of water gives supportA cell full of water gives support

The water carries useful dissolved mineralsThe water carries useful dissolved minerals

Balancing water loss with water Balancing water loss with water uptakeuptake

Plant adaptations to reduce water lossPlant adaptations to reduce water loss

Leaves have a waxy cuticle covering the Leaves have a waxy cuticle covering the upper epidermisupper epidermis

Most stomata are found on the lower Most stomata are found on the lower surface of the leaf where it is darker and surface of the leaf where it is darker and cooler.cooler.

Controlling water lossControlling water loss

How do plants reduce water loss?How do plants reduce water loss?

Stomata mainly on lower epidermisStomata mainly on lower epidermis Few stomataFew stomata Small leavesSmall leaves The ability to close stomataThe ability to close stomata

Balancing water loss with water Balancing water loss with water uptakeuptake

The stomata open and close automatically when supplies of water from the roots start to dry up.

Open stomata allow gases in and out for photosynthesis

Stomata are sensitive to light and close at night to conserve water.

Guard cells turgid Guard cells flaccid

Stoma opens Stoma closes

Stomatal peel Stomatal peel experimentexperiment

Paint the upper and lower surfaces of a leaf with nail Paint the upper and lower surfaces of a leaf with nail polish.polish.

Allow to dry.Allow to dry. Gently peel off and mount on a Gently peel off and mount on a

microscope slide.microscope slide. Place a cover slip on top and Place a cover slip on top and

examine under the microscope.examine under the microscope. How many stomata can you see?How many stomata can you see? Which side of the leaf has the most Which side of the leaf has the most

stomata?stomata?

PlenaryPlenary

Water, water Water, water everywhereeverywhereLearning objectivesLearning objectives Describe how water Describe how water

travels through a plant.travels through a plant. Explain that Explain that

transpiration is a transpiration is a consequence of the way consequence of the way leaves are adapted for leaves are adapted for photosynthesis.photosynthesis.

Explain how the cellular Explain how the cellular structure of a leaf is structure of a leaf is adapted to reduce adapted to reduce water losswater loss

Success criteriaSuccess criteria Student should be Student should be

able to draw a plant able to draw a plant showing the direction showing the direction of flow of water.of flow of water.

Successfully complete Successfully complete a stomatal peel.a stomatal peel.