Plant transport

Chapter 36

Plant transport

Evolutionary changesRoots, Leaves, StemsWaterCarbohydratesMineralsLight energyCO2

O2

Water transport

RootsXylemStomataTranspiration Cohesion & adhesion

Water transport

Flaccid:LimpWater lossPlasmolysis:Cell membrane pulls away from cell wallDue to water loss

Water transport

Turgid: FirmWater gainHealthier plant

Water transport

Cell to cell (short distance)Diffusion Apolplast:Continuum formed by cell wallsSymplast:Continuum formed by cytoplasm of cellsPlasmodesmata:Connection between cytoplasm

Cell wall

Cytosol

Apoplastic route

Symplastic route

Transmembrane route

Plasmodesma

Plasma membrane

Key

Apoplast

Symplast

Water transport

Root hairs absorb water & mineralsDiffuse into apoplast or symplastPass through cortexEndodermis (inner lining of cortex)Casparian strip (waxy substance)Controls flow water/ions to xylem Forces flow to pass cell membrane

Casparian strip

Plasmamembrane

Apoplasticroute

Symplasticroute

Roothair

Epidermis

Cortex

Endodermis

Vessels(xylem)

Stele(vascularcylinder)

Xylem

Movement based on bulk transportTranspiration:Negative pressureRoot pressure: Positive pressureUpward push of water/ions in xylemSolar powered

Xylem

Guttation:Loss of liquid through leavesEnds of leaves Increased root pressure

Stomata

H2O loss

CO2 intake

Guard cells

Opening & closing of the stomataDependent on turgor pressure of guard cellsThicker inner cell layerCauses bowing of the cell when turgidOpens the stomata

Guard cells

Active K+ pumpIncreased K+ in the guard cellsIncrease in H2O in the guard cells

TurgidStomata opensDecreased K+ leads to decreased H2O

Flaccid, stomata closes

Translocation of Phloem Sap in Spring

Translocation of Phloem Sap in Summer

Carbohydrate movement

Phloem (sieve-tube)Moves from source to nearest sinkCarbohydrates enter sieve-tube cellsActive transportCompanion cells & parenchyma cells provide the ATP

Phloem

Carbohydrate movement

Water potential differences-createdWater moves into the sieve-tube cells (osmosis)Increased turgorMoves carbohydrates to sink

Carbohydrate movement

Carbohydrates removed Active transportWater moves out (osmosis)Water diffuses back to xylemOr lost in transpiration