Celery is a good plant to use to show how nourishment is sucked out of the soil.

Take a whole celery and place it in a jug of water. Add red food colouring to the water.

Over the next few hours the stems will start to show the red colouring as water is taken from the jug and into the stem. Then the colour spreads to the leaves.

In time the whole plant will turn red, showing how water reaches every part of it.