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 Transport A. 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 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. 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 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