After destarching, a partly-covered leaf in sunlight tested with iodine shows
AThe whole leaf turning blue-black evenly
BOnly the exposed area turning blue-black
COnly the covered area turning blue-black
DNo part of the leaf turning blue-black
Answer & Solution
Correct answer: B. Only the exposed area turning blue-black
1. Photosynthesis cannot occur in the dark area under the cover.
2. Only the lit area produces starch.
3. Iodine binds with starch and turns blue-black.
4. So only the exposed area turns blue-black.
_Source: Selina Concise Biology Class 10, Ch on Photosynthesis (Mistral OCR'd PDF), section on starch test_
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