Biology Experiments / Photosynthesis – Starch Test (Iodine)

Photosynthesis – Starch Test (Iodine) Experiment

Perform the iodine starch test on a variegated leaf to prove photosynthesis requires light and chlorophyll.

Biology Class 6-8 Life-processes Intermediate
Prelab Brief
To test for the presence of starch in a leaf and prove that light and chlorophyll are necessary for photosynthesis using the iodine test.
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Theory

Perform the iodine starch test on a variegated leaf to prove photosynthesis requires light and chlorophyll. To test for the presence of starch in a leaf and prove that light and chlorophyll are necessary for photosynthesis using the iodine test.

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Formula

Principle: To test for the presence of starch in a leaf and prove that light and chlorophyll are necessary for photosynthesis using the iodine test.

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Aim

To test for the presence of starch in a leaf and prove that light and chlorophyll are necessary for photosynthesis using the iodine test.

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Apparatus

  • Potted plant (destarched for 48 hrs in dark)
  • Black paper and clips
  • Beaker with water
  • Beaker with alcohol (ethanol)
  • Bunsen burner / hot plate
  • Iodine solution
  • Petri dish
  • Forceps
  • Water bath
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Procedure

  1. Destarch the plant by keeping it in a dark cupboard for 48 hours.
  2. Cover part of a leaf with black paper secured with paper clips.
  3. Place the plant in sunlight for 4–6 hours.
  4. Pluck the leaf and boil it in water for 5 minutes to kill cells and stop reactions.
  5. Transfer the leaf to a beaker of alcohol and heat in a water bath until the leaf turns pale/white (chlorophyll removed).
  6. Remove the leaf, rinse with water, and spread it flat in a petri dish.
  7. Add iodine solution drops over the entire leaf.
  8. Observe: the exposed area turns blue-black (starch present); the covered area stays brown/yellow (no starch).
Pre-Lab Questions
What is the main aim of the Photosynthesis – Starch Test (Iodine) Experiment?
Which principle is demonstrated in the Photosynthesis – Starch Test (Iodine) Experiment?
What apparatus is required for this experiment?
Why is Potted plant (destarched for 48 hrs in dark) used in this experiment?
What formula or relationship is verified in this experiment?
What precaution should be followed while performing this experiment?
What conclusion can be drawn from the Photosynthesis – Starch Test (Iodine) Experiment?

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