Question

Explain an activity to test the presence of starch in a leaf.

Answer 1

To test leaves for the presence of starch,the leaf is boiled in water and then the boiled leaf is placed in a boiling tube containing 90% ethanol (ethyl alcohol). The ethanol boils and the green colouring (chlorophyll) is removed from the leaf. The iodine reagent is then added, which causes the green areas on the leaf, where starch is supposedly present, to turn to a blue-black colour. This indicates the presence of starch in the leaf.