Translocation occurs in phloem tissue

Steps:

• Identify leaf structures in the cross-section: epidermis, mesophyll, vascular bundle (xylem and phloem).
• Recall translocation definition: transport of sugars (sucrose) and amino acids from sources to sinks.
• Locate vascular bundle where transport happens.
• Pinpoint phloem as the site for downward and lateral movement of organic compounds.

Why B is correct:

• Phloem conducts translocation via mass flow driven by pressure gradients, as per the pressure-flow hypothesis.

Why the others are wrong:

• A: Epidermis provides protection, not transport.
• C: Xylem transports water and minerals upward, not sucrose or amino acids.
• D: Mesophyll is for photosynthesis, not translocation.

Final answer: B