masss transport in plants Flashcards
what does the xylem do
transports water and minerals from roots to rest of plant
explain xylem structure
long, dead, hollow cells with no end cell walls.
what does lignin do
provide strength and support
how does water enter root hair cells
osmosis
how is water potential in root hair cells kept low
they are actively up taking minerals
how does water evaporate through leaves
through the stoma
how does water move from xylem to stem
water evaporates through leaves leaving behind a low water potential. this triggers a transpiration pull. water moves up xylem into leaves via osmosis. creates cohesion tension.
what is cohesion tension
tension is a sucking force, cohesion is how water molecules are attracted to eachother by strong hydrogen bonds.
Use your understanding of the mass flow hypothesis to explain how
pressure is generated inside this phloem tube.
sucrose actively transported into phloem. reduces water potential. more water moves in by osmosis
describe the cohesion-tension theory of water
-water lost from leaf because of transpiration
-lowers water potential
-water is pulled up xylem creating tension
-water molecules stick together by strong hydrogen bonds
-this forms a continuous column
describe the mass flow hypothesis for the mechanism of translocation
-sucrose actively transported into phloem
-atp produced by companion cells
-lowers water potential in sieve cells
-water enters cell by osmosis
-increases hydrostatic pressure
-causes mass flow to sink
what are the three components of phloem vessels
-sieve tube elements. form a tube to transport sucrose in the form of sap
-companion cells. involved in atp production for loading of sucrose
-plasmodesmata. gaps between cell walls to link cytoplasm.
