When performing the starch test with variegated leaves what section of the leaf could serve as a control in this experiment and why?

Variegated leaves have areas that are white in color
instead of being green. This is due to a lack of plastids that contain chlorophyll;
without chlorophyll photosynthesis cannot take place.

The
areas of the leaves which are green produce monosaccharides through photosynthesis and
this is stored as starch.

If a starch test is being
performed on a variegated leaf, the white areas can serve as the control areas. The
starch test would be used to determine if there is a proper production of starch in the
green areas and to test if the conditions under which the plant is kept are appropriate
for this. The white areas would give a negative result no matter under what conditions
the plant is kept. The result obtained from the green areas can be compared against
this.