Lug’s solution is used to test for the presence of which substance in plant tissue?

Prepare for the NLN PAX Science Exam with flashcards and multiple choice questions. Each question includes hints and detailed explanations to boost your confidence and exam readiness.

Multiple Choice

Lug’s solution is used to test for the presence of which substance in plant tissue?

Explanation:
Lug’s solution detects starch because starch has a helical structure that iodine fits into. When iodine from the solution encounters starch, it lodges inside the helical turns of amylose and forms a blue‑black complex, so the tissue that contains starch turns that color. If starch isn’t present, the solution stays its usual brownish color. This test doesn’t reveal proteins, lipids, or simple sugars, which require different reagents to indicate their presence. In plant tissue, starch is stored in granules, so a blue‑black stain is a sign of starch storage.

Lug’s solution detects starch because starch has a helical structure that iodine fits into. When iodine from the solution encounters starch, it lodges inside the helical turns of amylose and forms a blue‑black complex, so the tissue that contains starch turns that color. If starch isn’t present, the solution stays its usual brownish color. This test doesn’t reveal proteins, lipids, or simple sugars, which require different reagents to indicate their presence. In plant tissue, starch is stored in granules, so a blue‑black stain is a sign of starch storage.

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