Activity 6.1 NCERT class 10 science chapter 6 Life processes
Procedure: Activity asks us to put a variegated leaf plant (e.g., Money plant) in the dark for three days, and in sunlight for a few hours. Then It asks to treat it with boiling alcohol and iodine solution.
Observation: Only the green coloured part of the leaf got the blue colour with the iodine solution while the white portion of the money plant leaf did not get the blue colour.
Inference: Only the green part of the leaf photosynthesize and make starch.
A variegated leaf contains green as well as a non-green part. The green part contains chlorophyll, while the non-green part is devoid of chlorophyll.
To begin with a fresh experiment, we put Leaf in the dark for a few days. Leaf in the dark do not photosynthesize new starch, and the plant consumes all its previous starch.
Now the leaf is put into the sun. Here chlorophyll inside the chloroplast makes new starch. A broken leaf can not transport starch to different parts of the body. So this starch now remains localized to the green area only.
We now put the leaf into boiling alcohol. A boiling solution of alcohol breaks the cell wall and chloroplast. This breakage washes the chlorophyll into the solution. As a result, leaf loses its green colour and become colourless. The colourless leaf is easy to stain with iodine.
Now, when we put this colourless leaf into an iodine solution, only the green part of the leaf turn blue.
In this experiment, we see that only the green part of the leaf turn blue with iodine. So, we can say only the green part of the leaf photosynthesize and produce starch. Since the green colour of the leaf is because of chlorophyll, we can also say that only chlorophyll-containing part of the leaf makes starch.
Ref: NCERT class 10 Science, chapter 6.