movement of water through roots
Uptake of Water by Roots Hairs
-- all water need to be absorbed due to the loss from transpiration.
-- they are efficient exchange surface becasue:
~they have a large surface are due to there being a lot of them & being very long.
~they have a thin cell surface therefore there is a short difusion pathway.
-- they are surrounded by soil consiting of a lot of water and mineral.
-- the soil has a high water potential compared to the root hairs.
-- therefore water moves in via osmosis.
-- water is then absorbed in the root hair cells in 2 way; apoplastic & symplastic pathway.
-- water drawn into endodermal cells pulling more water into the cells due to cohesive properties of water.
-- this causes tension that draws water along the cell walls of the root hair cells.
-- takes places in the cytoplsm to osmosis.
-- water pases between each cells via plasmodesma that contains cytoplasm.
-- the following cells always has a lower water potential so water is drawn in via osmosis.
Passage of Water into the Xylem
-- the casparian strip (a waterproof band) prevents further movement of water
-- water is forced into the xylem.
-- this is done due to salts and minerals being actively transported into the xylem causing a water potential gradient the water moves through via osmosis.
-- ^^ this is the root pressure ^^