Bulb's source-sink dynamics in tulip growth

Steps:

• Identify source as organ exporting photosynthates or reserves (e.g., bulb releasing stored nutrients early).
• Identify sink as organ importing resources (e.g., bulb storing post-photosynthesis).
• Analyze stages: Early growth (1-4) uses bulb reserves for shoot/leaf development, making it source; later stages (5-7) involve photosynthesis feeding bulb, making it sink.
• Match to options: Stage 4 aligns with peak vegetative growth (source); stage 7 with post-flowering storage (sink).

Why C is correct:

• Per plant physiology, sources export during resource demand (stage 4 vegetative expansion); sinks import during surplus (stage 7 bulbing), fitting tulip's bulb cycle.

Why the others are wrong:

• A: Stage 1 is dormant (neither); stage 5 involves active photosynthesis (bulb not sink only).
• B: Stage 3 is early sprouting (bulb source but not only); stage 6 is flowering (bulb mixed role).
• D: Stage 5 is reproductive (bulb not source only); stage 7 correct but pair mismatches.

Final answer: C