Describe an experiment to show that light is necessary for photosynthesis.

A destarched potted plant has one leaf partly covered on both sides with a strip of black paper, and the plant is left in sunlight for a few hours. The leaf is then tested for starch with iodine after removing its chlorophyll in warm alcohol. The uncovered part turns blue-black while the covered part does not, so starch has been formed only where light fell.

No citable source has been recorded for this record. Treat it as practice material, not as fact.

Explanation

Destarching the plant first is essential, or the starch found might have been there already.