Standard Science Primary 6 Energy

Plants are kept in a dark room for 48 hours. When tested with iodine solution, the leaves do not turn blue-black. Why?

A The plant has died from lack of air.
B The plant has used up its stored starch.
C The plant stopped taking in water.
D The plant converted starch into light energy.
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Worked Solution

Step 1: Photosynthesis requires light to make glucose/starch. Step [2-9]: In the dark, the plant cannot photosynthesize but still carries out life processes. Step [2-9]: It uses up its stored starch for energy, resulting in a negative iodine test.

Correct answer: The plant has used up its stored starch.

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