The leaf is boiled in water when testing for starch because boiling helps to soften the leaf tissue and break down cell walls, making it easier to extract the starch present in the leaf. This process also helps to release any starch granules that may be trapped within the cells, allowing them to be more easily detected with iodine solution. Additionally, boiling the leaf in water helps to denature enzymes that may break down starch during the testing procedure, ensuring more accurate results.
