Ch. 29 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. 29 Warm-Up

1. What is transpiration?

2. What are mycorrhizae?

3. What is the function of the Casparian strip?

Chapter 29Resource Acquisition, Nutrition, and Transport in

Vascular Plants

Plant Nutrition

Adaptations for Acquiring Resources

Shoots = capture light efficiently

Roots = acquire water and minerals

Nutritional Requirements

Essential element: required for plant to

complete life cycle and produce another

generation

Macronutrients (large amounts): CHNOPS +

K, Ca, Mg

◦Nitrogen = most important!

Micronutrients (small amounts): Fe, Mn, Zn,

Cu, etc.

Mutualistic Relationships:

1. Rhizobium bacteria supply nitrogen at roots

(fix atmospheric N2 to usable N)

• Plant supplies sugar & amino acids

2. Mycorrhizae (plant + fungus)

Role of soil bacteria in the nitrogen

nutrition of plants

Unusual nutritional adaptations:

epiphytes, parasitic plants, canivorous

plants

Epiphyte: grow on

surface of another

plant, absorb H2O from

rain through leaves

Parasitic Plants: not photosynthetic; absorb

sugar and minerals from living hosts

Carnivorous Plants: photosynthetic, but obtain

some nitrogen and minerals by digesting small

animals; found in nitrogen-poor soil

Transport Processes

Vascular Tissues: conduct molecules

Xylem Phloem

Nonliving functional Living functional

Xylem sap = H2O &

minerals

Phloem sap = sucrose,

minerals, amino acids,

hormones

Source to sink

(sugar made) to (sugar

consumed/stored)

Transport pathways in plant tissues:

Apoplast = materials travel between cells

Symplast = materials cross cell membrane, move

through cytosol & plasmodesmata

TRANSPORT OF WATER

Selectively permeable membrane: control

movement of substances in/out of cells

Osmosis: passive transport of water

Proton pump: active transport; uses E to

pump H+ out of cell proton gradient

Cotransport: couple H+ diffusion with

sucrose transport

Aquaporin: channel protein which

controls H2O uptake/loss

Review:

Solute transport

across plant cell

plasma membranes

Osmosis

**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 H2O in plant from regions of high

pressure low pressure

** Review AP Bio Investigation 4 (Osmosis & Diffusion)

Turgid: firm (healthy plant)

Flaccid: limp (wilting)

Plasmolysis: cell membrane shrinks & pulls

away from cell wall due to H2O loss; kills

most plant cells

Turgid Plant Cell Plasmolysis

Plant roots absorb essential elements

from soil

Root hairs: increase surface area of

absorption at root tips

Mycorrhizae: symbiotic relationship

between fungus + roots

◦ Increase H2O/mineral absorption

The white mycelium of the fungus ensheathes these roots of a pine tree.

Transport of H2O and minerals into xylem:

Root epidermis cortex [Casparian Strip]

vascular cylinder xylem tissue shoot system

Casparian strip controls entry into

vascular cylinder

How does material move vertically (against gravity)?

Transpiration: loss of H2O via

evaporation from leaves into air

Cohesion-tension hypothesis:

◦ Transpiration provides pull

◦ Cohesion of H2O transmits

pull from roots shoots

◦ Adhesion of H2O to xylem

walls (fight gravity)

◦ Negative pressure of xylem

sap (tension)

Stomata regulate rate of transpiration Stomata – pores in epidermis of leaves/stems, allow gas

exchange (CO2 in, O2 out) and transpiration (H2O out)

Guard cells – open/close stoma by changing shape

◦ Take up K+ lowers ψ take up H2O pore opens

◦ Lose K+ lose H2O cells less bowed pore closes

Cells stimulated to open by: light, loss of CO2 in

leaf, circadian rhythms

Stomata closure: drought, high temperature,

wind

BIOFLIX: WATER TRANSPORT

IN PLANTS

TRANSPORT OF SUGAR

Sugar Transport

Translocation: transport of sugars into phloem

by pressure flow

Source Sink

◦ Source = produce sugar (leaf photosynthesis)

◦ Sink = consume/store sugar (fruit, roots)

Via sieve-tube elements

Active transport of sucrose

Bulk flow by

positive pressure

flow in a sieve

tube

(active transport)

Material movement via

symplast is dynamic

Plasmodesmata allows movement of RNA &

proteins between cells

Phloem can carry rapid, long-distance electrical

signaling

◦ Nerve-like function

◦ Swift communication

◦ Changes in gene expression, respiration,

photosynthesis