Water movement in plants What is transpiration?

Starter: Look at these wet clothes, how are they going to dry?Even in winter?

Glossary

• Transpiration – the loss of water vapour from the leaves of plants through the stomata when they are open to allow gas exchange for photosynthesis.

• Done?Write down the word and symbol equation for photosynthesis.1) Where does each reactant come from?2) What happens to each product?

Plant Gas Exchange

Notes

• Carbon Dioxide enters through the stomata when they are opened.

• Air diffuses in and fills the spaces in the leaf along a concentration gradient.

• At the same time oxygen that has been produced diffuses out of the leaf down its concentration gradient.

• When the stomata are open, water also diffuses out…. Why is this potentially a problem?

• Gases move into and out of leaves through stomata – these can open and close depending on the time of day or year.

Lets investigate

• Celery!

Getting water in and out of a plant.

Lets look at some stomata….

Diagram of stomata and guard cells.

Transpiration in plants

A word from everybody's Fantasy Grandad

• http://www.youtube.com/watch?v=w6f2BiFiXiM

What features do roots have to allow effective uptake of water and minerals?

Lets investigate the rate of transpiration

Or Lets investigate

• Use a wick to model transpiration• Wick , boiling tube, drinking straw, blotting

paper and card.

• This represents the leaf transpiring.

• TASK: describe the model and relate it to transpiration in a real plant.

Look at these wet clothes, how are they going to dry?Even in winter?How can you increase the rate at which the laundry dries?

Factors that affect transpiration

Anything that increases PHS increases the transpiration rate.

Hot, dry and windy conditions also do- why?

Notes

• Transpiration is the loss of water vapour through the stomata in a leaf, causing the water to be pulled up the stem from the roots.

• Transpiration will increase in the day time as stomata are opened up to let CO2 in and O2 out.

• On a hot or dry day transpiration will also increase as there is a bigger water concentration gradient built up between the leaf and the atmosphere.

Water Tension

• Water constantly diffuses out of the plant leaves as there is less water outside the plant.

• Water moves down a Concentration gradient.

• Roots bring water into the plant bringing minerals into the plant. Water moves into the xylem vessels and through the plant

• Check out your celery.

Complete the adaptation sheet

• Done? Start the past paper questions.

Plenary

• Why do trees die when you cut through the bark all round the tree?