Phloem's Role in Downward Nutrient Transport

Steps:

• Bark contains phloem, the vascular tissue responsible for transporting organic compounds like sugars produced in leaves.
• Removing the phloem ring girdles the tree, blocking downward flow of these nutrients.
• Without nutrients reaching the roots, the tree cannot sustain growth or storage, leading to death.
• This matches option B, as phloem specifically handles organic nutrient transport to roots.

Why B is correct:

• Phloem conducts organic nutrients (e.g., sucrose) from photosynthetic sites in leaves to non-photosynthetic parts like roots, per the pressure-flow hypothesis.

Why the others are wrong:

• A: Mineral salts move upward through xylem, unaffected by phloem removal.
• C: Oxygen reaches roots via diffusion through soil and cortex, not vascular transport.
• D: Water ascends through xylem via transpiration pull, independent of phloem.

Final answer: B