Question

Describe a simple experiment to demonstrate Carbon dioxide is essential for photosynthesis.

Answer 1

Hint: Green plants can perform photosynthesis in the presence of sunlight as they consume carbon dioxide and release oxygen as the product. Therefore it is advised to plant more trees where the carbon dioxide concentration is very high.

Complete answer:
Here are steps of the experiment;
Select a potted healthy plant with long and narrow leaves. Keep this plant in mark for about two to three days. This step will ensure that the leaves are free from starch present.
Now, take a wide mouth jar or a glass bottle covered with cork to close the mouth of the bottle.
Now, split the cork into two vertically on the day of experiment.
Take 5-10 millilitres of potassium hydroxide solution in the bottle. This potassium hydroxide will absorb all the CO2 present in the glass bottle.
Now, in the early morning, insert one half of the selected leaf into the bottle through the split cork without plucking or cutting it from the plant.
On the other hand, the other part of the leaf is to be left outside the cork bottle. This bottle is needed to be kept airtight so we apply grease over the mouth of the bottle.
Now test this leaf for starch with the help of iodine solution.

Observation:- We will observe that the part of the leaf which was inside the bottle does not change colour and turns into deep blue. However the part of the leaf that was present outside the bottle turned into blue and prepared starch.

Note: Both halves of the leaf received the same amount of water and sunlight and both had chloroplasts however the portion of the leaf that was present inside the jar could not receive carbon dioxide.