what is the procedure to test the presence of starch
Answers
Answer:
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.
Answer:
The presence of starch in leaves can be tested by the Iodine test. When we remove chlorophyll from the leaf by boiling it in alcohol and then put two drops of iodine solution, it is colour change to blue indicates the presence of starch.
Explanation:
Starch is a white, powdery substance consisting of glucose which is used by plants as food. The presence of starch in leaves is evidenced enough of the process of photosynthesis being carried out in leaves as the formation of starch necessitates photosynthesis.
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
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