In an experiment to show that light is essential for photosynthesis, a plant was destarched, one of the leaves from the plant was tested to see if it was completely destarched (as shown in the diagram to test for the presence of starch), and the middle part of the leaf was covered with a black paper strip. The leaf was then exposed to sunlight for 2 to 3 days and a procedure to test whether starch was present was performed (as shown in the diagram to test for the presence of starch. The part not covered with the black paper strip is referred to as the ...