Potato Tuber as Source and Sink in Plant Physiology

Steps:

• Recall that a source in plants exports sugars (e.g., during sprouting when tuber supplies nutrients).
• Recall that a sink imports and stores sugars (e.g., during tuber formation when it accumulates reserves).
• Identify stages from context: assume stage 2 is sprouting (tuber as source), stage 4 is tuberization (tuber as sink).
• Match to options: B pairs source in 2 and sink in 4.

Why B is correct:

• It aligns with the definition of source-sink relationship, where tubers export during dormancy break (stage 2) and import during growth (stage 4).

Why the others are wrong:

• A: Reverses roles; stage 1 (early growth) is typically sink, not source.
• C: Stage 3 (dormancy) is source, but pairs sink with 2 (sprouting, actually source).
• D: Stage 4 is sink, but pairs source with 1 (formation, actually sink).

Not enough information on exact stage definitions to confirm without diagram.

Final answer: B