| The given diagram shows a destarched, variegated leaf, partly covered by black paper. The plant is placed in bright light for several hours. |
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| Four discs are then cut from the leaf in the positions shown and are tested for starch. Which discs do/does not contain starch? |
A) 1, 3 and 4 only
B) 1 and 2 only
C) 2 only
D) 3 and 4 only
Correct Answer: A
Solution :
Only the disc 2 in the figure shows positive test for starch. This is because it contains chlorophyll and is receiving sunlight to synthesise food by photosynthesis. The discs 1 and 3 do not contain chlorophyll, thus, will not perform photosynthesis. Disc 4 is destarched and is covered by black paper. It contains chlorophyll but is not receiving sunlight to carry out the process of photosynthesis hence, cannot synthesise starch.
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