Biochemical tests on root xylem tissue

Steps:

• Identify Y as xylem vessels in the root section photomicrograph.
• Benedict's solution tests for reducing sugars; xylem is composed of dead, empty cells lacking sugars.
• Iodine solution tests for starch; xylem does not store starch granules.
• Both tests therefore produce negative results.

Why D is correct:

• Xylem vessels are lignified, dead conduits without cytoplasm or storage compounds, so no reducing sugars (for Benedict's) or starch (for iodine) are present.

Why the others are wrong:

• A: Indicates reducing sugars present, but xylem contains none.
• B: Indicates starch present, but xylem stores no starch.
• C: Indicates both sugars and starch present, but xylem has neither.

Final answer: D