Question

Experiment to show that chlorophyll is essential for photosynthesis

Answer 1

But colored patches of variegated leaf doesn't include chlorophyll and thus don't prepare starch through photosynthesis. So iodine added in this region will change into brown color. Thus this experiment proves chlorophyll is necessary for leaves to prepare starch through photosynthesis

Answer 2

Q: Is chlorophyll necessary for Photosynthesis ?
A: Since it is not possible to remove chlorophyll from a leaf without killing it, so it
becomes necessary to use a leaf where chlorophyll is present only in patches.
Such a leaf is known as variegated leaf and a plant with such leaves is used in
this experiment.
For destarching the leaves, the potted plant is kept in a dark place for a couple of
days and then exposed to daylight for a few hour. The leaf is then removed from
plant. Its out line is carefully drawn to note the position of presence or absence of
chlorophyll on it. Now iodine is applied to the leaf to test for the presence of
starch. (Startch whenever come in contact with iodine turns blue).
This test shows that only those parts which were previously green turned blue
with iodine while the white parts turned brown. This result indicates that starch is
formed only in those parts of the leaf where chlorophyll exists (i.e. green parts).
In other words, photosynthesis is not possible without chlorophyll. If this were
possible the white parts of the leaf should have also given a blue colour with
iodine.