Explain the activity with diagram to shown that carbon dioxide is essential for photosynthesis.

Explanation

(i) Take two healthy potted plants which are nearly the same size.
(ii) Keep them in a dark room for three days.
(iii) 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.
(iv) Take two separate bell - jars and cover both plants with them.
(v) To seal the bottom of the jars to the glass plates use vaseline so that the setup is air tight.
(vi) Now place the plants in sunlight for about two hours.
(vii) Pluck a leaf from each plant and check for the presence of starch.
(viii) Leaf from plant A shows absence of starch whereas leaf from plant B tests positive for startch.

Experimental set up (a) with potassium hydroxide (b) Without potassium hydroxide.