BRAINCAKEApoplast Pathway
The second route for water across the root cortex is the apoplast pathway. The apoplast is the system of cell walls and the spaces between cells.
Cellulose cell walls are made of fibres with water-filled spaces between them. Water moves through these spaces and through the gaps between cells without entering the cytoplasm. As water is pulled up the xylem, the cohesion between water molecules pulls more water along the cell walls behind it.
Because no membranes are crossed and there is little resistance, the apoplast pathway is faster than the symplast pathway and carries most of the water across the cortex.
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Key terms in this lesson
- water potential
- A measure of the tendency of water molecules to move out of a solution; water moves from a higher to a lower (more negative) water potential.
More in Transport in Plants
- Evidence for the Movement of Water Through Xylem
- Phloem
- Root Hair Cells
- Symplast Pathway
- Transpiration
- Cohesion-Tension Theory
- Adhesion and Capillarity
- Modelling Transpiration
All 21 lessons in Transport in Plants · All Edexcel AS-level Biology topics