Question

Explain that sunlight is essential for photosynthesis.

Answer 1

Hint: Photosynthesis is the process of preparing the food in presence of sunlight, water by the plants, as the plants prepare the food on their own, so they are called photoautotrophs or primary producers of the ecosystem.

Complete answer:
Plants use the process called photosynthesis, in order to make food.
During photosynthesis, plants trap the light from the sun and utilize the energy of the light.
Where this trapped light energy is used to convert to chemical energy and combine the water and carbon dioxide into glucose, which is used by the plants as their food.
Where some energy is used to produce other substances such as cellulose and starch and this stored food is utilized by plants later.

Experiment to show that sunlight is important for photosynthesis.
The requirements for the experiments are:
- 2 plants
- Glass jar or beaker.
- Stove and pan.
- Ethyl alcohol.
- Iodine.
- Hot water and tweezer.

Procedure:
- Before the test begins, two plants are taken and placed in 2 different rooms, one is under sunlight and another one is in a dark room for 24 hours.
- After 24 hrs, ethyl alcohol is taken to fill the glass jar or beaker and place this jar on the pan, place them on the stove and start heating the ethyl alcohol.
- And in the meantime, the leaves of both plants are cut and placed in the hot water with the help of a tweezer.
- Now the leaves are again placed in ethyl alcohol for 120 seconds.
- Because of the ethyl alcohol, the leaves are turned to white color, and now the iodine solution is dropped on the leaves and wait for the observation.

Observation:
- The ethyl alcohol breaks the chlorophyll in the leaves and makes them white in color, and iodine turns the starch into a blue-black color.
- So the leaves which contain starch are turned into blue-black, and the leaf without starch is turned to reddish-brown color.
- The leaf which turned blue-black is a leaf which is placed in sunlight, and photosynthesis occurred and starch was produced.
- So starch is produced only in the leaves which are exposed to sunlight, and this proves that sunlight is very essential for plants to do photosynthesis.

Note: In this experiment, the main reason for the removal of chlorophyll from the leaves is, their presence may mask the color produced by the iodine and may mislead the experiment, so it is very important to decolorize the leaves for this experiment to know the presence of starch.