Why may young leaves that are just emerging from the bud be considered "sinks" for phloem transport?

Question

Quizplus · Accepted Answer

Young leaves that are just emerging from the bud are still growing and developing, so they require more carbohydrates than they are producing through photosynthesis. Therefore, they are considered "sinks" for phloem transport, as they consume more carbohydrates than they produce. Once the leaves mature and begin producing more carbohydrates through photosynthesis, they become "sources" for phloem transport.

Why May Young Leaves That Are Just Emerging from the Bud