Here's why:
* Phloem is a vascular tissue, much like xylem, which carries water and nutrients.
* Xylem moves water and minerals upwards from the roots to the rest of the plant.
* Phloem moves sugars, produced during photosynthesis in the leaves, downwards to the roots, stem, and other parts of the plant for growth and storage.
The phloem consists of specialized cells called sieve tubes which are connected end-to-end. These tubes have pores that allow the sugar solution to flow through. The movement of sugars through the phloem is driven by a pressure gradient, much like the movement of water through xylem.
