======Test for Starch in Leaves======


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**Alternative titles:** Photosynthesis Starch Indicator Test
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====Summary====                   
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====Procedure====  
  -Place one healthy potted plant in a dark place for about 24 hours to remove stored starch; keep a second, similar plant in bright light.
  -After 24 hours, pick one leaf from each plant.
  -Set up a hot water bath by placing a beaker or jar with ethyl alcohol inside a saucepan of water; heat the pan gently until the alcohol is hot (near boiling). Turn off heat.
  -Using tweezers, dip each leaf in hot water for about 60 seconds to soften and kill the tissue.
  -Transfer the leaves into the hot alcohol until they turn pale or nearly white (chlorophyll removed).
  -Rinse the decolorized leaves briefly in cool water to soften them and lay them in a shallow dish.
  -Cover each leaf with iodine solution and observe the color change.
  -Record which leaf turns blue-black (starch present) and which remains yellow-brown (little or no starch).



====Links==== 
Experiment: To test a leaf for starch - Science Projects: 
{{youtube>_rCjKTgAxgE?}}\\

Use iodine to test a leaf for starch - KClassScienceChannel: 
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📄 Test for Starch in Plants - Home Science Tools: [[https://learning-center.homesciencetools.com/article/test-for-starch-photosynthesis/]]\\

📄 Testing a leaf for starch - BBC Bitesize: [[https://www.bbc.co.uk/bitesize/guides/zpcvbk7/revision/3]]\\

====Variations====
  *Cover part of a leaf with opaque foil while in light to show starch only forms in exposed regions.
  *Compare different light intensities or colors during the 24-hour light period.
  *Extend the dark period (e.g., 48 hours) and test whether starch disappears completely.
  *Test leaves from different plant species or from sun versus shade leaves on the same plant.




====Safety Precautions====
  *Adult supervision required when using hot water and heated alcohol.
  *Heat ethyl alcohol only in a water bath; keep away from flames and sparks (alcohol is highly flammable).
  *Use heat-resistant glassware and handle hot containers with tongs or gloves.
  *Wear safety glasses, gloves, and a lab apron; iodine can irritate skin and stain clothing.
  *Ensure good ventilation and keep lids on alcohol when not in use.
  *Dispose of iodine and alcohol according to local guidelines; do not pour large amounts down the drain.




====Questions to Consider====
  *Why decolorize the leaf before adding iodine? (Removing chlorophyll makes the iodine color change easy to see.)
  *What does a blue-black iodine result indicate? (Starch is present, meaning photosynthesis produced and stored carbohydrates.)
  *Why keep one plant in the dark first? (To use up stored starch so any new starch must come from photosynthesis during light exposure.)
  *How does covering part of a leaf affect staining? (Covered areas receive no light, produce little or no starch, and stay yellow-brown.)