Question

Leaves contain starch justify the statement with test

Answer 1

Make sure the leaf is completely covered with iodine. m Watch for a few minutes to see if a blue-black colour develops in any part of the leaf. A blue-black colour with iodine solution indicates that starch is present. n Wash your hands to remove any traces of plant sap, or the chemicals that you have used.

Answer 2

Procedure

The video above shows the steps in Testing a Leaf for the Presence of Starch. The Procedure outlined below is slightly different.


Remove a green leaf from a plant that has been exposed to sunlight for a few hoursHalf-fill a 250cm3 beaker with water. Heat the water until it boils. Keep the water at boiling point.Use the forceps to place the leaf in the boiling water. Boil for 2 minutes.Turn off the Bunsen Burner. (If you are using a heat source without a naked flame - electric water bath or hot plate - this step is unnecessary.)Place the boiled leaf in a boiling tube containing 90% ethanol.Place the boiling tube in hot water and boil for 10 minutes or until the leaf decolourizes.    ( It may be necessary to replace the ethanol)Gently remove the leaf and wash with a fine trickle of cold tap water.Spread the leaf evenly on a white tile.Add a few drops of iodine/potassium iodide solution to the leaf and note any observations.

Observations/Results

The leaf was flaccid (soft) after being boiled in waterThe ethanol changed from colorless to greenThe leaf was brittle after being boiled in ethanolThe leaf become flaccid once more after being rinsed in cold waterAfter iodine solution was added...



Observation

No color change (Iodine Solution remains brown)

Iodine/Potassium Iodide solution changed from brown to blue- black