Plant Transport Flashcards
What is the difference between transport in short distance and long distance?
short distance: diffusion or active transport
long distance: bulk flow
What do proton pumps do?
create a hydrogen ion gradient that is a form of potential energy (can be harnessed to do work)
contributes to a voltage: membrane potential
How is the membrane potential useful?
drives the transport of solutes into the cell
contributes to the absorption of K+ by root cells
When do cotransport occur?
when a transport protein couples the diffusion of one solute H+ with the active transport of another NO-
What is water potential?
a measurement that combines the effects of solute concentration and pressure
determines the direction of water movement (moves from high potential to low potential)
What is solute potential?
also called the osmotic potential
proportional to the number of dissolved molecules, more solutes makes it more negative
What is pressure potential?
the physical pressure on a a solution
What is the water potential equation?
Psi = Psi solute + Psi pressure measured in MPa
What are the three routes for transport?
Transmembrane route
Symplastic route
Apoplastic route
What is the transmembrane route?
out of one cell, across a cell wall, and into another cell
What is the symplastic route?
via the continuum of the cytosol
What is the apoplastic route?
via the cell walls and extracellular spaces
Where does most water and mineral absorption take place?
near the root tips, where the epidermis is permeable to water
What is the Casparian Strip? What does it do?
a waxy strip of the endodermal wall
it blocks apoplectic transfer of minerals from the cortex to the vascular cylinder
What does the endodermis do?
regulates and transports needed minerals from the soil into the xylem
How do plants lose most of their water?
through transpiration, evaporation of water from the plants surface
What is lost water replaced by?
replaced by bulk flow of water and minerals, called xylem sap, from the steles of roots to the stems and leaves
How is root pressure generated?
at night, transpiration is low
root cells still pump mineral ions into the xylem of the vascular cylinder, lowing water potential
water flows in from the roots cortex, causes root pressure
What is guttation?
water is pushed out through leaves from roots
What is the transpiration-cohesion-tension mechanism?
water is pulled upward by negative pressure in the xylem
water vapor in airspaces of leaf moves down water potential gradient and exits the leaf via stomata, which lowers the Psi in the mesophyll
transpiration produces negative pressure (tension) in the leaf, which exerts a pulling force on water in the xylem, pulling water into the leaf
How is transpirational pull facilitated?
by cohesion of water molecules to each other and adhesion of water molecules to the cell walls.
What part of the plant is water attracted to?
cellulose in xylem cell walls
What prevents the xylem from collapsing?
thick walls of trachea and vessels
What controls the diameter of stoma?
guard cells
