• # question_answer Advika took a Croton plant with shaded leaves and set up an experiment as shown here. She kept the plant first in darkness for a few hours and then placed it in sunlight. After 6 hours, she performed iodine test on plucked leaves P, Q and R. Which of the following is n the possible outcome? (Note: Shaded portion in the question figure indicates green colour and in the options, it indicates blue-black colour.) A)                              B) C)                           D)

Iodine gives blue-black colour with starch. Only green parts of the leaf prepare food (starch). In leaf 'P', starch will not be synthesized as $C{{O}_{2}}$is needed for preparing food, so iodine will not show any change in colour. In leaf 'R', the exposed part of the leaf will give positive result with iodine while the covered part will give negative        I result. In leaf 'Q', green part will show change in colour i.e., it will turn blue black performing iodine test.