To demonstrate that chlorophyll is necessary for photosynthesis.

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 •  First of all take a potted plant, like croton, which has variegated leaves, 

i.e partly green and partly non- green. 

•  Now keep the plant in a dark place for about three days so that all starch gets used up. 

Now keep the plant in bright sunshine for three to four days. 

•  Pluck a leaf from the plant and mark the green area in it and trace them on a sheet of paper. Now the leaf is boiled in water and then immersed in warm 90% alcohol solution, so the green parts of the leaf get decolourised. 



                                                       

•  After washing the leaf in water, pour some iodine solution over the colourless leaf and observe the change in colour of the leaf and compare this with the tracing of the leaf done in the beginning. 


                             

Question. What do you conclude about the presence of starch in various areas of leaf.           

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