Iodine solution is used to test leaves for the presence of starch. You need to:
1.heat a plant leaf in boiling water for 30 seconds (this kills the leaf, stopping any chemical reactions)
2.add the leaf to boiling ethanol in a water bath for a few minutes (the boiling ethanol dissolves the chlorophyll and removes the green colour from the leaf - it turns white so it is easy to see the change in colour)
3.wash with water to rehydrate and soften the leaf and spread onto a white tile
4.add iodine solution from a dropping pipette
After a few minutes, the parts of the leaf that contain starch turn the iodine from brown to blue/black.
Set up one plant on a sunny windowsill and another in a dark room for 24 hours
After 24 hours, fill a beaker with ethyl alcohol and place it in a saucepan full of water
Continue heating the pan until ethyl alcohol starts boiling and then take it off from the heat
With the help of tweezers, dip each of the leaves in hot water for a minute
Now, dip the leaves in the beaker holding ethyl alcohol for 120 seconds or till they change their color to almost white
Place each of them in a shallow dish
Cover these leaves with some drops of iodine solution and observe
Observation:
Alcohol breaks down the chlorophyll and hot water kills the leaf. Hence, the leaf is no more green in color
When leaves are treated with iodine, one of them turns its colour to blue-black due to the presence of starch with iodine as an indicator. The other leaf turns its colour to reddish-brown
The leaf that was kept in light turns blue-black in colour indicating the leaf has been carrying out photosynthesis, producing starch
Answers & Comments
Answer:
Iodine solution is used to test leaves for the presence of starch. You need to:
1.heat a plant leaf in boiling water for 30 seconds (this kills the leaf, stopping any chemical reactions)
2.add the leaf to boiling ethanol in a water bath for a few minutes (the boiling ethanol dissolves the chlorophyll and removes the green colour from the leaf - it turns white so it is easy to see the change in colour)
3.wash with water to rehydrate and soften the leaf and spread onto a white tile
4.add iodine solution from a dropping pipette
After a few minutes, the parts of the leaf that contain starch turn the iodine from brown to blue/black.
Explanation:
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Verified answer
Answer:
Requirements:
Sample plants
Glass jar or beaker
Stove and saucepan
Iodine solution
Ethyl alcohol
Tweezer
Procedure:
Set up one plant on a sunny windowsill and another in a dark room for 24 hours
After 24 hours, fill a beaker with ethyl alcohol and place it in a saucepan full of water
Continue heating the pan until ethyl alcohol starts boiling and then take it off from the heat
With the help of tweezers, dip each of the leaves in hot water for a minute
Now, dip the leaves in the beaker holding ethyl alcohol for 120 seconds or till they change their color to almost white
Place each of them in a shallow dish
Cover these leaves with some drops of iodine solution and observe
Observation:
Alcohol breaks down the chlorophyll and hot water kills the leaf. Hence, the leaf is no more green in color
When leaves are treated with iodine, one of them turns its colour to blue-black due to the presence of starch with iodine as an indicator. The other leaf turns its colour to reddish-brown
The leaf that was kept in light turns blue-black in colour indicating the leaf has been carrying out photosynthesis, producing starch
Explanation:
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