MCQ
Iodine stains:
  • A
    Pectin
  • B
    Lignified regions
  • C
    Cellulose
  • Starch.

Answer

Correct option: D.
Starch.
Iodine is used in chemistry as an indicator for starch. When starch is mixed with iodine in solution, an intensely dark blue colour develops, representing a starch/iodine complex.
Starch is a substance common to most plant cells and so a weak iodine solution will stain starch present in the cells. Iodine is one component in the staining technique known as Gram staining, used in microbiology.

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