A leaf that is not all green
This experiment needs no destarching, no polythene and no chemicals. The plant has already set it up for you.
You need
A leaf from a plant with variegated leaves — white croton, or a variegated vada — a sheet of white paper, and the materials for the starch test.
Method
- Take a leaf from a plant with variegated leaves and record its pattern of variegation on a sheet of white paper.
- Then carry out the starch test on that leaf.
Why you draw it first
The starch test destroys the very thing you need to know. Boiling the leaf in alcohol takes out the chlorophyll, and once the green is gone there is no way to tell which parts of the leaf were green to begin with. The drawing is the record of the leaf before the test, and without it the result afterwards means nothing.
The control is built into the leaf
Every other experiment in this chapter needed two leaves and a great deal of care to make them comparable. Here the green part and the white part of one leaf have shared the same stalk, the same water, the same air and the same sunlight for the whole of their lives. Nothing could be better matched.
The white parts are not dead, and they are not damaged
A variegated leaf is a perfectly healthy leaf whose cells do not all make chlorophyll. The white tissue is alive and is being fed by the green tissue beside it. That is the only difference between the two regions, and it is exactly the difference the experiment tests.