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Home / Science projects / Photosynthesis: Testing for Starch
  • Photosynthesis: Testing for Starch

    Photosynthesis: Testing for Starch

    Any extra food a plant makes through photosynthesis is stored in its tissue as starch. Testing a leaf for starch is one way to test whether it has been performing photosynthesis. (Adult supervision required.)

    What You Need:

    What You Do:

    1. Put one of the plants in the dark for 24 hours; leave the other one on a windowsill.
    2. After 24 hours, put some ethyl alcohol in a beaker and place that in a saucepan full of water. Heat the pan until the ethyl alcohol begins to boil. Remove from the heat.
    3. Use tweezers to dip each of the leaves in the hot water for 60 seconds. Then place them in the beaker of ethyl alcohol for two minutes or until they turn almost white. Set them each in a shallow dish.
    4. Cover the leaves with some iodine solution and watch.

    What Happened:

    The hot water kills the leaf and the alcohol breaks down the chlorophyll, taking the green color out of the leaf. When you put iodine on the leaves, one of them will turn blue-black and the other will be a reddish-brown. Iodine is an indicator that turns blue-black in the presence of starch. The leaf that was in the light turns blue-black, which demonstrates that the leaf has been performing photosynthesis and producing starch.

    Try the test again with a variegated leaf (one with both green and white) that has been in the sunlight. A leaf needs chlorophyll to perform photosynthesis — based on that information, where on the variegated leaf do you think you would find starch?

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By: tricia phillips
Date: Nov 24, 2014

where on the leaf did it turn blueblack? and why was the plant destarched prior to the experiment?

By: Brayoh
Date: Nov 09, 2014

Wow , an excellent explanation

By: D
Date: Nov 06, 2014

I know a way to see if food has starch!

By: Ephraim
Date: Nov 06, 2014

Thnx for ur enlightenment. I’m grateful to you. Pls i need more updates

By: skylar morgan
Date: Oct 13, 2014

this is great.
i done it at home and it actually worked i feel like an actual scientist
i always been interested in plants and now i can see what is inside.
u know we need plants to survive because they give us oxygen so we can breath if not the we could all die.
plants r one of the main features in life they teach us what is inside and how they can make food with only sunlight .
also when the best temperature best or night or day is when we should keep them out.
also how to keep them alive

By: Toree teez
Date: Oct 09, 2014

Our teacher using this site as his guideline…....I will benifite from this site….. may you send me the latest observatoin??????

By: abel kalungwana
Date: Sep 22, 2014

Briefly explain how you would test the necessity of chlorophyll in a variegated leaf.

By: Jake
Date: Sep 04, 2014

thanks, I knew that iodine showed starch but the alcohol and water part was new to me and very helpful

By: onesmo william
Date: Jul 21, 2014

that starch was present in surch way due to the observertion the colour change to blue black.

By: britney
Date: Jul 15, 2014

thaxxxx i hav benefited alot its just like i learnt from school