Water Transport in Plants: Xylem

Water is essential for photosynthesis, for maintaining cell turgor and for transporting dissolved minerals throughout the plant. This lesson explains how water moves from the soil, through the roots, up the stem and into the leaves via the xylem. Understanding the transpiration stream and the structure of xylem vessels is a key part of Edexcel GCSE Biology (1BI0) Topic 6.

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The Journey of Water Through a Plant

Water follows a continuous pathway called the transpiration stream:

1. Water is absorbed from the soil by root hair cells through osmosis
2. Water moves across the root (from cell to cell by osmosis) to the xylem vessels in the centre of the root
3. Water travels up the xylem in the stem
4. Water moves into the leaf through the xylem in the veins
5. Water evaporates from the surfaces of mesophyll cells into the air spaces inside the leaf
6. Water vapour diffuses out through the stomata — this is transpiration

This continuous flow from roots to leaves is driven by the evaporation of water from the leaves.