Starch formation and photosynthesis - what is the relationship?

Procedure: The plant is placed somewhere dark, e.g. a cupboard, for 3 days. It’s essential that the plant is watered beforehand.

After removing the plant from the cupboard, covering a leaf with dark paper or aluminum foil and another part of a leaf - possibly with perforations - and hold it in place with paper clips (Fig 1A). Alternatively, an aluminum foil envelope (with a distinctively shaped hole in the centre) may be placed over both sides of the leaf, and the edges of the hole pinched in a little so that light only reaches the exposed part of the leaf.

Expose the potted plants to sunlight for a day.

After wards, boil 200 ml of water. Cut 3 leaves: one that was covered with aluminum foil, one which was partially covered and another which was uncovered.

Place each leaf in the boiling water for 1-2 minutes or until soft and limp. Prepare a water bath and put it inside a beaker with alcohol and heat it gently until boiling. Introduce the leaves one by one in alcohol until they become whitish in color, then immerse them in cold water. Put a little iodine water in three glass (Petri) dish. Spread out the leaf. Wait a few minutes for color to develop. Look at and record the results.