Transport in PlantsTransport in Plants

• What are the 3 levels of transport?

• Transport of materials into individual cells

• Cell to cell transport

• Long distance transport

I.I. Cellular TransportCellular TransportA. Passive Transport:A. Passive Transport:

• Driven by principles of diffusion

• Much of the diffusion is facilitated

• Selective channels are usually gated and regulated

B. Active TransportB. Active Transport

• Proton pump,

• Generates membrane potential and stored potential energy.

• Transport of many other molecules is regulated via the proton pump

C. Water Potential and C. Water Potential and OsmosisOsmosis

• Water moves from high to low water potential

• If a flaccid cell is placed in a hypertonic environment in what direction will there be net water movement? What happens to the plant cell?

• Plant loses water into the solution• Cell plasmolyzes

AquaporinsAquaporins

• 1990’s scientists discover water pores in membranes that facilitate the diffusion of water

• Water still diffuses through lipid bilayer• Aquaporins speed up this diffusion• Aquaporins may have gated channels

that allow for water regulation regardless of surroundings

TonoplastTonoplast

• Membrane that surrounds central vacuole

• Has proton pumps

II. Lateral TransportII. Lateral Transport

• How do cells transport water and minerals from soil into the steele of the root?

• Move from cell to cell individually

• Symplast transport

• Apoplast transport

Assistants in root absorptionAssistants in root absorption

• Root hairs increase surface area• Mycorrhizae

enhance mineral absorption• Endodermis functions as selective

region• Casparian strip is waxy and

hydrophobic, traps water and mineral into the vascular tissue

III. Long Distance Transport:III. Long Distance Transport:A. Root Pressure: PushingA. Root Pressure: Pushing

• Water loss from leaves is low at night• Roots are still taking up minerals and

water• Water and minerals flowing into the

steele dispalces fluid in the steele (xylem sap), up.

• This root pressure causes guttation; dew.

B. Transpiration: PullingB. Transpiration: Pulling

• Water is adhesive and cohesive

• As one droplet moves the one next to it also moves

• As water is lost out of stomata, water below it moves up

• Negative pressure pulls the water up and out of the plant.

IV. Control of TranspirationIV. Control of Transpiration

• Guard cells regulate water loss

• What conditions will promote closing of guard cells?

• Hot, dry, windy conditions

• Photorespiration increases as water loss decreases.

• What environmental streses cause stomata to close during the day?– Water loss– Abscisic acid signals– Increase in temp

• What adaptations are seen for arid climates?– Small thick leaves– Depress stomata– Shed leaves druing dry part of year– Store water in stems (cacti)

• How does CAM metablosim help reduce transpiration rate?– Assimilate CO2 at night, so can close stomata in

day

V. Translocation: Phloem V. Translocation: Phloem TransportTransport

• Sugar source is where sugar is stored or made

• Sugar sink is where sugar will be stored or used

• Sugar made at source is loaded into sieve tube members for transport.