Cambridge O Level Biology · Syllabus 5090 · Transport in Flowering Plants
Transpiration Stream
What is Transpiration Stream?
The continuous movement of water through a plant, from the soil into the root hair cells by osmosis, across the root cortex cells, into the xylem, up the xylem vessels as an unbroken column, and into the mesophyll cells of the leaf, from whose moist surfaces it evaporates into the leaf air spaces before diffusing out through the stomata as water vapour. The stream is drawn upwards by the transpiration pull created when water is lost from the leaf, not pushed upwards by the root.
This definition is part of the Transport in Flowering Plants chapter in Cambridge O Level Biology.
Last reviewed Syllabus 2026-2028