Let us take a leaf from a plant well exposed to sun light.
Boil the leaf in methylated spirit over a water bath.It becomes pale-white due to the removal of chlorophyll.Observe the leaf.
  Take the leaf carefully from the test tube by using a brush.
   Spread the leaf in a petridish and add a few drops of tinture iodine/betadine solution on it.Again observe the leaf.
  The presence of starch will be indicated by a blue - black color.
1) Pluck a green leaf from a plant . 
2) Boil the leaf in alchohol to remove the green pigment chlorophyll from it .
3) Wash the decolourised leaf to remove any chlorophyll sticking to it .
4) Pour dilute iodine solution from a dropper over the decolourised leaf .
5) Appearance of blue black colour in leaf shos the present of starch in it.