Transport in Plants

What are the 3 levels of transport? Transport of materials into individual

cells Cell to cell transport Long distance transport

I. Cellular TransportA. Passive Transport:

Driven by principles of diffusion Much of the diffusion is facilitated Selective channels are usually gated

and regulated

B. 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 Osmosis

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

Aquaporins

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

Tonoplast

Membrane that surrounds central vacuole

Has proton pumps

II. Lateral Transport

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

Move from cell to cell individually Symplast transport Apoplast transport

Assistants 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:

A. 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

stele displaces fluid in the stele (xylem sap), up.

This root pressure causes guttation; dew.

B. 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 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 stresses 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 during dry part of year Store water in stems (cacti)

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

day

Xerophytes – adapted to arid climates

V. Translocation: Phloem Transport

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.

Using an aphid to tap into phloem sap