The tissue in trees that transports sugars made by photosynthesis is phloem.
Photosynthesis produces sugars, especially sucrose, in leaves. Phloem moves these dissolved organic compounds from “source” tissues, such as mature leaves, to “sink” tissues, including roots, growing shoots, seeds, and fruits. This movement is called translocation.
A common mix-up is xylem. Xylem mainly carries water and dissolved minerals upward from the roots, while phloem carries sugar-rich sap between sources and sinks. Phloem transport can move in different directions in different sieve tubes, depending on where the plant needs nutrients.
Phloem is living tissue made largely of sieve-tube elements supported by companion cells. In trees, much of the active phloem lies near the inside of the bark. The name comes from the Greek word phloios, meaning “bark,” and botanist Carl Nägeli introduced the term in 1858.