- A Sucrose levels stay uniform across plant organs through the year in the majority of documented cases
- B Source and sink depend on current sugar export versus import, not on fixed anatomy
- C Phloem sap direction is set permanently by gravitational pull as widely reported
- D Phloem moves sugars downward mainly, in a fixed one-way direction according to most studies
Correct answer: B. Source and sink depend on current sugar export versus import, not on fixed anatomy
Explanation: A source is any organ that is a net exporter of sugars (e.g., mature leaves), while a sink is a net importer (e.g., roots or developing fruits); the same organ, like a storage root, can switch from sink to source depending on the season.
Concept context
Water and mineral absorption, the ascent of sap, transpiration, and phloem transport via the pressure flow hypothesis.