Describe an experiment to show that carbon dioxide is necessary for photosynthesis.

A destarched potted plant has one leaf enclosed in a flask containing potassium hydroxide solution, which absorbs carbon dioxide, while another leaf is left in the air. The plant is left in sunlight for some hours and both leaves are then tested with iodine. The leaf in the air turns blue-black, showing starch, while the leaf in the flask does not.

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

Explanation

The plant must be destarched first, by keeping it in the dark for two days, so that any starch found is newly made.