The green pigment, known as chlorophyll, can be effectively removed from leaf cells by using a method that involves boiling the leaf first in water and then in ethanol.
Removing the green pigment from a leaf is a common process in plant experiments, often done to visualize other pigments or to test for the presence of starch after photosynthesis. The key is to dissolve the chlorophyll out of the plant tissue.
Steps to Remove Chlorophyll from a Leaf
Based on standard laboratory procedures, including the method described, the process involves two main stages:
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Killing the Leaf:
- Action: Heat a plant leaf in boiling water for approximately 30 seconds.
- Purpose: This crucial first step kills the leaf cells, stopping any ongoing chemical reactions, such as photosynthesis. It also helps to soften the leaf's cell walls, making it easier to extract the chlorophyll in the next step.
-
Extracting the Chlorophyll:
- Action: Add the leaf to boiling ethanol in a water bath for a few minutes.
- Purpose: The boiling ethanol acts as a solvent for chlorophyll. As the leaf sits in the hot ethanol, the chlorophyll dissolves into the ethanol, drawing the green colour out of the leaf.
- Safety Note: Ethanol is highly flammable. Heating it directly over a flame is dangerous. Therefore, the ethanol is heated indirectly by placing its container in a bath of boiling water (a water bath). This allows the ethanol to reach its boiling point safely.
- Result: As the chlorophyll is removed, the leaf will turn a pale white or yellowish colour, making it easy to see that the green pigment is gone.
This two-step process ensures that the leaf is prepared for the extraction and that the chlorophyll is successfully dissolved by the ethanol.
Summary Table
| Step | Action | Purpose |
|---|---|---|
| 1. Kill Leaf | Heat leaf in boiling water (approx. 30 seconds) | Stops chemical reactions, softens cells |
| 2. Extract Chlorophyll | Add leaf to boiling ethanol in a water bath (few mins) | Dissolves chlorophyll out of leaf cells (leaf turns white) |
By following these steps, the green colouration caused by chlorophyll can be effectively removed, leaving the leaf decolorized and ready for further analysis, such as testing for starch with iodine solution.
