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Science

Transport in plants

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Plants have two different types of 'transport' tissue. Xylem transports water and solutes from the roots to the leaves, phloem transports food from the leaves to the rest of the plant. Transpiration is the process by which water evaporates from the leaves, which results in more water being drawn up from the roots.

Plant transport

No heart, no blood and no circulation, but plants do need a transport system to move food, water and minerals around. They use two different systems – xylem moves water and solutes from the roots to the leaves – phloem moves food substances from leaves to the rest of the plant. Both of these systems are rows of cells that make continuous tubes running the full length of the plant.

Xylem

Xylem cells have extra reinforcement in their cell walls, and this helps to support the weight of the plant. For this reason, the transport systems are arranged differently in root and stem – in the root it has to resist forces that could pull the plant out of the ground. In the stem it has to resist compression and bending forces caused by the weight of the plant and the wind.

Plant stem

A cross section of a plant stem

Stem – the xylem and phloem are arranged in bundles near the edge of the stem to resist compression and bending forces.

Comparison of xylem and phloem

TissueProcessWhat is movedStructure
XylemTranspirationMoves water and minerals from roots to leavesColumns of hollow, dead reinforced cells
PhloemTranslocationMoves food substances from leaves to rest of plantColumns of living cells

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