Xylem vs. Phloem: What's the Difference?

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Xylem carries water and dissolved minerals upward from the roots to the leaves, while phloem carries the sugars made in photosynthesis to wherever the plant needs them. Xylem is built mostly from dead, hollow, lignified cells and is pulled by evaporation from the leaves. Phloem is made of living sieve tubes and moves food in either direction, using pressure differences.

At a glance

	Xylem	Phloem
What it carries	Water and dissolved minerals	Sugars (mainly sucrose) and other food
Direction	One way: roots up to the leaves	Both ways: from sources to sinks
Cells	Vessels and tracheids, dead when mature	Living sieve tubes with companion cells
Driving force	Transpiration pull from evaporating leaves	Pressure flow driven by loading sugar
Energy use	Movement itself needs no cell energy	Loading sugar uses ATP

Which should you use?

Xylem

Xylem is at work when a wilted potted plant perks up after watering, and it forms most of the wood in a tree trunk such as a teak or neem.

Phloem

Phloem is at work when sugar made in sugarcane leaves is carried down and stored in the stem, or when a potato plant fills its tubers with starch.

Frequently asked questions

Why does xylem not need living cells?

Water in xylem is pulled up by tension, not pumped. As water evaporates from leaf pores, cohesion between water molecules drags the column upward, so hollow dead tubes with strong lignin walls work best and do not collapse under the pull.

What are sources and sinks in phloem transport?

A source is a part that makes or releases sugar, such as a mature leaf; a sink is a part that uses or stores it, such as a root, fruit or growing shoot. Phloem flows from source to sink, so its direction can change with the season.

Where are xylem and phloem found in a plant?

They run together in vascular bundles through roots, stems and leaf veins. In a typical dicot stem, xylem lies towards the centre and phloem towards the outside, which is why removing a ring of bark cuts off food supply to the roots.