Will a leaf taken from a potted plant kept in a dark room for a few days turn blue-black when tested for starch? Give reasons for your answer.

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Solution

Iodine test:
Confirmatory test for sugar presence.
Forms blue-black suspension on interaction.
Potted plant in dark:
Will not have undergone photosynthesis.
No starch production as this is the end product of photosynthesis.
Stored starch exhausted in a few days.
No remaining starch in the leaves of the plant.
Hence, the leaf will never turn blue-black when tested for starch.

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