bulk_flow.html: 36_13XylemSapFlow_L.jpg
Bulk flow is the movement of fluid in vessels.
cell_transport.html: 36_08CellTransport.jpg
The plasma membrane and vacuolar membrane provide transmembrane transport.
The cytoplasmic continuum, connected by plasmodesmata
, is the symplast route.
The continuum of cell walls plus extracellular spaces provide the apoplast route.
guttation.html: 36_11Guttation.jpg
Guttation.
Root pressure is forcing excess water from this strawberry leaf.
mycorrhizae.html: 36_10Mycorrhizae.jpg
Mycorrhizae, symbiotic associations of fungi and roots.
The white mycelium of the fungus ensheathes these roots
of a pine tree.
The fungal hyphae provide an extensive surface area for the absorption of water and minerals.
pressure_flow.html: 36_18PressureFlow.jpg
Pressure flow in a sieve tube.
Sap moves through a sieve tube by bulk flow driven by positive pressure
.
The building of pressure at the source end and reduction of that pressure at the sink end cause
water to flow from source to sink, carrying the sugar along.
proton_pump.html: 36_03ProtonPump.jpg
Proton pumps provide energy for solute transport.
By pumping H+ out of the cell with the hydrolysis
of ATP, proton pumps produce an H+ gradient and a charge separation called a membrane potential.
These two forms of potential energy can be used to drive the transport of solutes.
proton_transport.html: 36_04PlantCellSoluteTrans.jpg
Solute transport in plant cells.
The role of proton pumps in transport is an application of chemiosmosis,
using a transmembrane proton gradient to link energy–releasing processes to energy–consuming processes in cells.
redwood.html: 36_01Redwoods.jpg
root_transport.html: 36_09RootLateralTransport.jpg
Lateral transport of minerals and water in roots.
stomata.html: 36_15GuardCellFunction.jpg
The mechanism of stomatal opening and closing.
sucrose_load.html: 36_17SucroseLoading.jpg
Loading of sucrose into phloem. | ||
---|---|---|
Sucrose made in the mesophyll travel the symplast. Some sucrose exit the symplast and accumulate in sieve-tube members and companion cells via the apoplast. | (b) | Proton pumps generate an H+ gradient, driving sucrose accumulation in the cell by chemiosmosis . |
transpirational_pull.html: 36_12Transpiration.jpg
The generation of transpirational pull in a leaf.
The negative pressure at the air–water interface in the leaf is the physical basis of transpirational pull,
which draws water out of the xylem.
turgid.html: 36_07Turgor.jpg
Turgor loss in plants causes wilting, and can be reversed when the plant is watered.
Video:
Elodea in differential interference contrast microscopy.
vascular.html: 36_02VascPlantTransport.jpg
The vascular system
allows plants to distribute specialized funstions to different parts and grow to great heights.
water_animals.html: ../ch07/07_13WaterBalanceA.jpg
.
water_plants.html: 36_06CellVEnvPsi.jpg
In a hypertonic (low external Ψ) environment, the cell loses water and plasmolyzes. | In a hypotonic (high external Ψ) environment, there is net uptake of water by osmosis, the cell becomes turgid which helps it ertain its shape. |
water_potential.html: 36_05WaterPotential.jpg
Water moves across a selectively permeable membrane from higher water potential to lower.
Water potential (Ψ) is the sum of pressure potential (ΨP) and solute potential (ΨS): Ψ = ΨP + ΨS.
ΨP = 0 MegaPascal at at sea level and room temperature.
xylem_sap.html: 36_13XylemSapFlow_L.jpg
Ascent of xylem sap.
Hydrogen bonding
forms an unbroken chain of water molecules from leaves to the soil,
by cohesion among water molecules and adhesion of water molecules to cellulose.
The force that drives the ascent of xylem sap is a gradient of water potential (Ψ),
mainly pressure potential ( ΨP).
Transpiration results in the ΨP at the leaf end of the xylem being lower than the
ΨP at the root end.