Question

How would you test the presence of starch in leaves?

Answer 1

Hint: Leaf is a flat green portion that arises from the stem of a vascular plant. Leaves play a major role in the process of photosynthesis. Photosynthesis can be studied in order to demonstrate the development of starch and the value of chlorophyll.

Complete answer:
Starch is a type of carbohydrate. Plants have the ability to convert the glucose produced during photosynthesis to starch which is then stored for the future. Plants convert them into glucose when needed for respiration.

In general, an iodine test is made to check for the presence of starch in leaves. This process is very simple, that every student can do it at home. Take a fresh leaf from any plant nearby. Boil the leaf in hot water, such that it becomes very soft and tender. This makes the cells of the leaf also to become soft. Also, try to heat the leaf in ethanol solution also to remove most of its colour. After this wash the leaf in plain water and spread it to dry. Lastly add a few drops of iodine solution on the leaf. After a few minutes, the areas of the leaf containing starch turn blue-black.

Notice that ethanol is heated by a hot water pump. Ethanol boils at 78 ° C, such that the tubing of ethanol boils when put in a beaker of hot water. This is safer than using a Bunsen burner since ethanol is flammable.

Note:Green plants absorb light in their leaves and turn it to photosynthesis energy. Temperature, carbon dioxide concentration and light intensity can influence the photosynthesis rate.