Water begins by moving into the root hair cells via osmosis down a water potential gradient.
Ions move in by active transport.
Ions move with water by either the symplast or apoplast pathway.
Symplast pathway: Movement through cell cytoplasm
Apoplast pathway: Movement through cell walls.
Travel down a water potential gradient through
pathways via osmosis along the cortex until reaching the endodermis where
apoplast is restricted so all water and ions must enter
cytoplasm.
Apoplast is restricted by casparian strip (waterproof strip)
Ions are then actively transported into xylem to
lower water potential to allow water to travel
through via osmosis
water creates hydrostatic pressure which helps push it up the xylem
Xylem - cells with broken down
horizontal cell walls strengthened
by lignin to make thick hollow
'pipes'
Water is pulled up via tension of the
continuous unbroken column of water due
to hydrogen bonds occuring between
molecules
This is mass/bulk transport
To reach the leaf osmosis occurs via apoplast or symplast
pathways and then transpiration occurs.
Transpiration: Evapouration from the surface of
mesophyll cells into air spaces then diffusion out
through open stomata.
Lost water is then replaced by
adjacent cells via pathways, so
more water is pulled from xylem
to replace loss and repeats.