[Campbell Biology P.849] Which of the following statements about sugar sources and sinks in ... | Practice Question

Which of the following statements about sugar sources and sinks in plants is correct?

  • A: Growing roots are always considered sugar sources.
  • B: A storage organ like a tuber can function as both a sugar source and a sugar sink depending on the season.
  • C: Mature leaves always act as sugar sinks.
  • D: Expanding leaves primarily function as sugar sources.

Explanation

The text states that a storage organ, such as a tuber or a bulb, may be a source or a sink, depending on the season. When stockpiling carbohydrates in the summer, it is a sugar sink. After breaking dormancy in the spring, it is a sugar source because its starch is broken down to sugar, which is carried to the growing shoot tips. Growing roots and expanding leaves are sugar sinks as they consume sugar for growth, while mature leaves if well illuminated are sugar sources.