Science - Year 3/4B Spring 2 Plants Greatly Green Growers Session 5 Teaching PowerPoint © Original resource copyright Hamilton Trust, who give permission for it to be adapted as wished by individual users. We refer you to our warning, at the foot of the block overview, about links to other websites.

What does our experiment tell us? The coloured water has travelled up the stems to the leaves and flowers. But how?

We know the water started in the vase and travelled up the stem first and from there to the leaves and flowers. But how does it travel?

Look at your sections of celery. What do you notice? There are coloured circles stained by the water. What might these circles be? They are the cut ends of long tubes that run up the length of the stem, a bit like tiny drinking straws.

If you look at the side of your stem of celery you will notice that there are ridges. These ridges are made by the tubes that run all the way up the stem. The tubes are called xylem and it is their job to carry water up to the leaves and flowers. This is why you saw the leaves and flowers change colour.

Every stem, whether thick or thin, has tubes of xylem inside to transport water up through the plant. Tree trunk A tree makes a new ring of xylem each year which is why you can count the rings on a tree stump to find out how old it is.

What does water do in the leaves? Remember we have already learnt that water is one of the ingredients a plant uses to make its food. Can you remember the other one? It is a gas in the air called carbon dioxide

It is the leaves where food is made. The energy comes from … sunlight

Flowers and stems need water too, to keep them healthy. Flowers without water will quickly droop. This is called wilting.

Does water ever leave the plant? Yes, water escapes into the air through the tiny holes on the underside of the leaves. This water is in the form of vapour (a gas) which is invisible.

If you tie a plastic bag around some leaves on a plant, after a while it will fog up because of the escaping water vapour. This is rather like water vapour escaping from your lungs when you breathe out.