Mohl's half leaf experiment

Experiment to demonstrate Moll’s half-leaf experiment for showing that CO₂, light, chlorophyll and water are necessary requirements for photosynthesis:

Requirements:

A potted plant, caustic potash, wide- mouthed bottle, iodine, split cork, water

Method:

1. De-starch a potted plant by putting it in complete darkness for two days.

2. Fill partly a wide-mouthed bottle with strong solution of caustic potash and fit a split cork on its mouth.

3. Insert about half of the portion of a leaf of the de-starched plant into the bottle through the split cork (Fig. 36).

4. Place the whole apparatus in light after applying grease on the upper portion of split cork, and test the leaf for stach after about 10 hours.

Observations:

Portions of the leaf inside the bottle as well as in between the split cork show negative test for starch indicating the absence of photosynthesis while the portions outside the split cork show positive test for starch indicating the presence of process of photosynthesis in this region.

Results:

Negative starch test by the leaf portion present inside the bottle indicates that process of photosynthesis is absent in this region. This portion of leaf is getting all the essential requirements, i.e., light, chlorophyll and water except the CO₂ because the latter is absorbed by the caustic potash. Thus, it can be concluded that CO₂ is necessary for this process.

Precautions:

1. The half leaf kept inside the bottle should not touch the KOH solution. 

2. The apparatus should be kept air tight by applying grease Or baseline.