The chemical substance used to test the presence of starch in the cell of a leaf is ________.

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Solution

Starch:
Plants perform photosynthesis and produce glucose.
Glucose is stored in the plant in the form of starch.
To experimentally show that photosynthesis has occurred, iodine solution is added to treated leaves.
If photosynthesis has occurred then on addition of iodine solution, blue-black colouration is seen.
This colouration is seen due to the reaction of iodine with starch.
If photosynthesis has not occurred then on addition of iodine solution, blue-black colouration is not seen as starch is absent.
Final answer : The chemical substance used to test the presence of starch in the cell of a leaf is iodine.

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