Question

Moll’s half leaf experiment is performed to show that:
A. Light is needed for photosynthesis
B. Chlorophyll is needed for photosynthesis
C. Oxygen is evolved during photosynthesis
D. Carbon dioxide is needed for photosynthesis

Answer 1

Hint:
As you know there are some certain requirements for every reaction to take place and photosynthesis is one of those reactions. Moll was a scientist who performed an experiment to prove that carbon dioxide is required for the process of photosynthesis to make food.

Complete answer:
The Moll’s half leaf experiment is popularly known to be performed to demonstrate the necessity of carbon dioxide for the process of photosynthesis to form starch.
In this experiment half part of one leaf is inserted into a corked bottle containing KOH solution. The plant is then placed in sunlight for a few hours. The leaf is then tested for starch with iodine solution. When this experiment is performed under controlled conditions, the following results are observed.
When the leaf was tested in the lab for the presence of starch, the part of the leaf which was in a bottle and split cork tested negative for starch, which indicates the absence of photosynthesis. In contrast the portions outside the split cork show positive tests for starch showing the presence of the process of photosynthesis in this region.
Results: Negative starch test by the leaf present inside the bottle indicates that the process of photosynthesis is absent in this region. This portion of leaf is getting all essential requirements such as light, chlorophyll and water except the carbon dioxide, as it is absorbed by the caustic potash. Negative test of starch which is also shown by the leaf present in split cork is due to lack of carbon dioxide as well as light, which clearly conveys that both of them are essential requirements.

Note:
Positive test for starch shown by the leaf present outside the bottle shows that photosynthesis is continuously going on there because of availability of all the necessary requirements whereas it is absent in the region where one component that is carbon dioxide was absent.