Lecture AP Biology Chapter 36 Resource acquisition and transport in vascular plants

After studying this chapter you will be able to understand: The role of passive transport, active transport, and cotransport in plant transport; the role of diffusion, active transport, and bulk flow in the movement of water and nutrients in plants; how the transpiration cohesiontension mechanism explain water movement in plants; how pressure flow explains translocation.

Ch 36 Warm-Up

1. Describe the process of how H2O

gets into the plant and up to the leaves.

2. Compare and contrast apoplastic

flow to symplastic flow.

3. Explain the mass flow of materials

in the phloem (source to sink).

Ch 36 Warm-Up

1. What is transpiration?

2. What are mycorrhizae?

3. What is the function of the

Casparian strip?

Chapter 36

Resource Acquisition and Transport in Vascular Plants

What you need to know:

 The role of passive transport, active

transport, and cotransport in plant

transport.

 The role of diffusion, active transport, and bulk flow in the movement of water and nutrients in plants.

 How the transpiration cohesion-tension mechanism explain water movement in plants.

 How pressure flow explains

translocation.

What does

a plant need?

 Selectively permeable membrane:

osmosis, transport proteins, selective

Solute transport across plant cell

plasma membranes

 ** Water potential (ψ): : H2O moves from high

ψ  low ψ potential, solute conc & pressure

◦ Water potential equation: ψ = ψS + ψP

◦ Solute potential (ψS) – osmotic potential

◦ Pressure potential (ψP) – physical pressure

on solution

◦ Pure water: ψS = 0 Mpa

◦ Ψ is always negative!

◦ Turgor pressure = force on cell wall

 Bulk flow: move H Bulk flow 2O in plant from regions

of high  low pressure

** Review AP Bio Investigation 4

Flaccid: limp (wilting)

Plasmolyze: shrink, pull away from cell wall (kills most plant cells) due to H2O loss

Turgid: firm (healthy plant)

Turgid Plant Cell Plasmolysis

A watered impatiens plant regains its turgor.

Vascular Tissues: conduct molecules

Nonliving functional Living functional

Xylem sap = H2O &

Transport of H2O and minerals into

xylem:

Root epidermis  cortex  [Casparian Strip] Casparian Strip]  vascular cylinder  xylem tissue  shoot system

◦ Increase H2O/mineral absorption

The white mycelium of the fungus

ensheathes these roots of a pine tree

Transport pathways across Cortex:

Apoplast = materials travel between cells

Symplast = materials cross cell membrane, move Symplast

through cytosol & plasmodesmata

Entry into Vascular Cylinder:

 Endodermis (inner layer of cortex) sealed

by Casparian strip (waxy material)

◦ Blocks passage of H2O and minerals

◦ All materials absorbed from roots enter xylem through selectively permeable

membrane

How does material move vertically (against

gravity)?

Transpiration : loss of H2O via

evaporation from leaves into air

1. Root pressure (least (least

important)

up

from rootsshoots

Guttation: exudation of water droplets seen in morning (not dew), caused by root pressure

Stomata regulate rate of transpiration

 Stomata – pores in epidermis of leaves/stems, allow gas exchange and transpiration

 Guard cells – open/close stoma by changing shape

◦ Take up K +  lower ψ  take up H 2 O  pore

opens

◦ Lose K +  lose H2O  cells less bowed  pore closes

Cells stimulated openopen by: light, loss of

CO2 in leaf, circadian rhythms

Stomata closureclosure: drought, high

temperature, wind

BIOFLIX: WATER

TRANSPORT IN PLANTS

Sugar Transport

phloem by pressure flow

Via sieve-tube elements

Active transport of sucrose

Bulk flow

in a sieve

tube