Transport of Water in
Plants
Movement of Water
Uptake by roots - enters xylem in roots
Moves up xylem in stem
Moves from xylem to leaf cells
Evaporates into air spaces in leaves
Transpiration of water through open stomata into the air
Transpiration Pull
Water is lost by transpiration from stomata
Replaced by water from the mesophyll layer
Constant loss of water creates a lower water potential in leaves
Water is pulled up the plant along a decreasing gradient
Action is similar to a straw
Cohesion-Tension Theory
Water molecules cling together by hydrogen bonds (cohesion)
Water molecules cling to xylem walls by hydrogen bonds (adhesion)
Cohesion creates a tension from the water molecules pulling other water molecules
Upward pull creates a tension that helps water uptake and movement up the plant
Creates a single, continuous, unbroken column of water
Root Pressure
Endodermis moves materials into medulla, lowering water potential
Water follows by osmosis, increasing pressure
Pressure forces water into the xylem and provides a weak push up the plant
Plants
Movement of Water
Uptake by roots - enters xylem in roots
Moves up xylem in stem
Moves from xylem to leaf cells
Evaporates into air spaces in leaves
Transpiration of water through open stomata into the air
Transpiration Pull
Water is lost by transpiration from stomata
Replaced by water from the mesophyll layer
Constant loss of water creates a lower water potential in leaves
Water is pulled up the plant along a decreasing gradient
Action is similar to a straw
Cohesion-Tension Theory
Water molecules cling together by hydrogen bonds (cohesion)
Water molecules cling to xylem walls by hydrogen bonds (adhesion)
Cohesion creates a tension from the water molecules pulling other water molecules
Upward pull creates a tension that helps water uptake and movement up the plant
Creates a single, continuous, unbroken column of water
Root Pressure
Endodermis moves materials into medulla, lowering water potential
Water follows by osmosis, increasing pressure
Pressure forces water into the xylem and provides a weak push up the plant
