Water transport Flashcards
(12 cards)
Symplast pathway 3
water moves through cytoplasm of the epidermal and cortical cells, initially entering the epidermal cells via osmosis and moving between adjacent cells through the plasmodesmata
Apoplast pathway
Water moves through cell walls of cells until it is blocked by the casparian strip
Vacuolar pathway
Water moves via cell vacuoles in cytoplasm
Why is apoplast mostly used
Bc of the polar nature of cellulose fibres and water molecules: adhesion between cellulose and water
why is vascuolar least commonly used
Water must move through several plasma membranes so there is alot of resistance
How do ions move into the xylem from the epidermal cells 3
Via apoplast route then actively transported into cells of endoderm to bypass casparian strip
Symplast route from then onwards to xylem req active transport
What is the advantage of the ions entering into the symplast route from the apoplast
Lowers the water potential of endodermal and pericycle cells causing water to enter them via osmosis to continue the symplast stream
which ions deliver nitrogen into plants
NO3- and NH4+
How does water enter the root from the soil and why
Water enters the root via osmosis bc water potential of soil is high, water potential of vacuoles in root is low bc of active uptake of mineral ions
What affect of pressure does water entering the root have
Creates hydrostatic pressure at the base of the xylem: root pressure
Transpiration?
loss of water vapour from leaves giving rise to the transpiration stream
What 4 factors affect Ro transpiration
Light intensity
Temp
Humidity
Air movement
