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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?


    Buy Testing For Starch Experiment Kit

    testing for starch kit


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Comments




By: Mike nyondo
Date: Jun 17, 2015

Please help how can l test starch in a cassava,

[HST adds:  Try this article on testing for starch in food.  http://www.hometrainingtools.com/a/thanksgiving-dinner-science-projects  Hope this helps!]


By: Snenhlanhla
Date: Jun 07, 2015

What is the hypothesis for this experiement?


By: pavaniswetha
Date: Jun 03, 2015

it was really good thank you for showing us this experiment


By: babangida abdullahi umar
Date: Jun 03, 2015

test for starch in bread test, observation, infrence


By: john
Date: Jun 02, 2015

this has realily helped me


By: shu
Date: Jun 01, 2015

why must we put one of the plants in the dark ??


By: Sam SammYzo
Date: Apr 20, 2015

It helped alot but a little confusin at the same time!


By: ashley henry
Date: Apr 12, 2015

I really need an experiment on the variegated leaf. Like really badly!!!!


By: natifa natasha moore
Date: Apr 06, 2015

love it


By: Kathy Rusert
Date: Feb 23, 2015

Is there a starch indicator other than iodine?  When I read the warnings, it seems pretty dangerous for upper elementary/middle school students to use and I am looking for a good substitute.