Test for starch in a leaf
The simple sugar formed during photosynthesis is converted into starch and stored in the leaves.
for starch in a leaf can be done through a simple procedure.Materials and Apparatus required for this process include:
- A leafy potted plant which has been kept in the dark for at least 5 hours
- Droppers, Beakers, Source of heat, Boiling tubes, Forceps, a tripod stand, Methylated spirit, Iodine solution and White tile
i. Boil water in a beaker.
ii. Detach one leaf from the potted plant.
iii. Dip the leaf in the boiling water for three minutes. This stops chemical activity/photosynthesis in the leaf.
iv. Remove the leaf from the hot water using forceps.
v. Put the leaf in the boiling tube containing methylated spirit and stand the tube in the beaker containing boiling water until all the green colour has been dissolved out of the leaf.
vi. Remove the leaf from the methylated spirit and dip it in warm water. This softens the leaf.
vii. Spread the leaf on the white tile.
viii. Add drops of iodine to cover the whole leaf.
ix. Record your observation.
Conclusion from starch test:
- A leaf in which photosynthesis took place would turn blue black. This color indicates the presence of starch in the leaf.
- Starch would have been formed from the sugar produced during photosynthesis.
- In the absence of starch there would be no color change.