describe an experiment to show that plants need sunlight ?
Answers
•Take two similar saplings.
• Keep one in dark room and another in adequate sunlight.
Observation:
You will see that the plant kept in darkness would cease to grow and probably die due to lack of glucose in it whereas the one kept in adequate sunlight nourishes itself.
Reason:
Plants need sunlight to carry out an essential process called photosynthesis, whose product is oxygen and glucose( stored as starch).
Without sunlight they will not be able to do so and eventually die.
Answer :-
Aim of the experiment :- To determine whether sunlight is important for plants or not.
Procedure :-
- Place a healthy green potted plant in a dark room for 1-2 days. This is done to ensure that the plant consumes all its reserve food and the leaves do not contain any starch left in them.
- Then, cover a portion of a leaf of the plant on both sides with two equally measured pieces of black paper, fixed in position with two paper clips.
- Now, expose this plant to bright sunlight.
- After a few hours, remove the leaf, decolourize it with alcohol and test the presence of food (starch) in the leaf with the help of a solution of Iodine.
Observation :- It can be observed that the portion of the leaf covered with black paper, does not show any presence of food (starch).
Conclusion :- The above phenomenon occurred because the food prepared by the plants is stored as starch.
Starch reacts with the iodine solution and gives blue-black colour.
Only those portions of the leaf which were exposed to sunlight, were able to photosynthesise and thus, appeared blue-black coloured after the iodine solution test.
The covered portion of the leaf didn't receive sunlight and couldn't photosynthesise thus, didn't appear blue-black in colour after being tested with iodine.
Thus, from the above experiment, it can be undoubtedly concluded that sunlight is essential for plants.