Apparatus Beaker Hot plate Test tube White tile Forceps Methylated spirits Iodine solution Leaf from a photosynthesising plant
Method: 1. Set up the apparatus as shown (diagram A). 2. Dip the leaf in the boiling water for one minute. 3. Place the leaf in some methylated spirits in a test tube. 4. Place the test tube into the boiling water until the leaf turns white (diagram B). Move the leaf gently up and down with the forceps.
5. Remove the leaf and rinse it in the hot water (diagram C) to soften it. 6. Spread the leaf on a white tile (diagram D) and cover it with drops of iodine. 7. Record your results. How do you know the leaf contains starch?
A Water B
Methylated spirits
Iodine C D
White tile Fig. 8 Testing a leaf for starch.
Questions Why do you think the methylated spirits turned green when the leaf was placed into the test tube? What is the function of this green pigment? What process produces the glucose that plants use to make starch? Where can starch be stored in a plant? Give examples to support your answer.
