Question

write the materials required and the procedure to prove that light is essential for photosynthesis

Answer 1

MATERIALS REQUIRED

A potted plant, black paper strips or Ganongs light screen, clips or cellotape, alcohol, iodine solution, water bath, beaker, burner, water, petri dish, dropper.

PROCEDURE

Select a healthy potted plant and destarch the plant by placing it in complete darkness for at least 48 hours.

After 48 hours, using clips or cellotape cover a part of the leaf of the plant from both upper and lower sides with black paper strips.

Now, keep the potted plant in sunlight for at least 3-4 hours.

After 3-4 hours, pluck the leaf and remove black paper strips.

Boil the leaf in water for about 2 minutes.

Now, to decolourise the leaf, transfer the leaf from boiling water to a beaker containing ethanol and boil the leaf in a water bath.

Remove the leaf from beaker and wash it in water at room temperature.

Place this leaf in petri dish and add few drops of iodine solution over the decolourised leaf.

The area of the leaf that was uncovered performed photosynthesis and will have starch, therefore turned blue-black with iodine solution.

The covered portion of the leaf remains yellow as it does not perform photosynthesis.

[Note: Ganong’s light screen can be used in place of black paper strip]