Take two healthy potted plants which are nearly the same size.
i) Keep them in a dark room for three days.
ii) Now place each plant on separate glass plates. Place a watch glass containing potassium hydroxide by the side of one of the plants. The potassium hydroxide is used to absorb carbon dioxide.
iii) Cover both plants with separate bell jars as shown in Fig.
iv) Use vaseline to seal the bottom of the jars to the glass plates so that the set-up is air-tight.
v) Keep the plants in sunlight for about two hours.
vi) Pluck a leaf from each plant and check for the presence of starch as in the above activity.
vii) Both the leaves show the presence of the same amount of starch.