Transport in Plants I

If you're not part of the solution, you're part of the precipitate.

-   Steven Wright

Business• Quiz: mean = last term, ~6/9 (not good enough),

– didn’t study enough,– studied, did well, with tinkering will master,– studied, but didn’t do too well,

• probably memorized terms, without grounding the words in reality.

• Midterm I: one week from Friday,– Essay questions due Tuesday afternoon, 3 pm.

• email to young@biol.wwu.edu,– Subject Line must say 206 Question,– Include your name, if your email address is esoteric,

• 2 extra credit point (maximum) if you provide at least one GOOD question, and email it, on time, and with correct subject line.

Not so Good Good Excellent

Rote Concept/Process oriented Question Integrated question, i.e spanning chapters

?

Today

• Introduction to Transport,

• Mechanisms of Transport,

– passive,– active,

• Questions, Extra Credit?

Transport

…molecular and ionic movement from one location to another,

– H2O,

– Sugars,

– Minerals,

– Gases,

– Other Macromolecules: proteins, RNA, hormones, etc.

Plant Transport(What’s Transported)

• H2O,

– uptake by roots, transport via xylem, loss to the atmosphere and metabolic process,

• Minerals (in solution),

– Uptake by roots, loss to senescence, herbivory, etc.

Xylem

Plant Transport(What’s Transported)

• Gases,

– CO2, O2, H2O.

– N2, ethylene, etc.

Stomates

Plant Transport(What’s Transported)

• Sugars,

• other organics,

– hormones, – amino acids,– etc.

Phloembydirecional

Plant Transport(What’s Transported)

• Roots, »

– uptake O2,

– discharge CO2.

Gas Exchange/Respiration

Plant Transport

Symplastic and ApoplasticEverything

Across Membrane(s)

First Then

What Drives Transport?

Gravity,

Pressure,

Electrical fields, (for charged substances),

Concentration gradients, (entropy-driven diffusion).

• Diffusion, by molecular motion,

– good only at short distances,

• Pump, Channel and Carrier mediated transport,

– small molecules across membranes,

• Osmosis (water across membranes),

• Bulk Flow,

– efficient large-scale, mass movement.

Mechanisms of Transportin organisms

• Diffusion, by molecular motion,

– good only at short distances,

Fick’s First Law“Uber Diffusion” (1855) Adolf Fick

Js = Ds

cs

x

flux densityflow rate

concentration gradient

change in distance

diffusion constant

Adolf Fick: Contributions

• Ophtalmotonometer – Intraocular pressure

• Aneroid manometer – Vascular grad (BP)

• Pneumograph – Peripheral thorax variation link

• Plethysmography – I/O of blood, air in lungs, etc.

• Dynamometer – Muscle output

• Laws of diffusion 1855

• Contact lens

Fick’s Law and Organisms

tc = 1/2 = L2

Ds

(tc = 1/2) for a molecule to move (p = 0.5) a set distance (L)...

… is equal to the distance (L) squared divided by the diffusion coefficient (Ds).

• Ds for sucrose is ~10-9 m2 s-1,

– 50 m: tc = 1/2 = 2.5 seconds,

– 1 m: tc = 1/2 = 32 years.

Fick’s Law and Organisms

Choleochaete orbicularis

50m

Trees ?Bryophytes

Chlamydomonas reinhardii

• Diffusion, by molecular motion,

– good only at short distances,

• Pump, Channel and Carrier mediated transport,

– small molecules across membranes,

• Osmosis (water across membranes),

• Bulk Flow,

– efficient large-scale, mass movement.

Mechanisms of Transportin organisms

Membranes

Plasma Membrane (1x),

Plastids (2x),

Mitochondria (2x),

Vacuole (1x),

Golgi, ER (1x),

Peroxisomes, etc. ( 1x).

Coordinated Transport

Arabidopsis Genome

Adapted from Biochemistry and Molecular Biology of Plants, pp. 115

H+ (protons) ATP synthase

ATP hydrolase (ATPase)

Transporters

- carriers, - channels.

ATP Pumpsall organisms

vacuolar organelles

P-Type ATPasesPhylogentic Family

Tree

P-Type ATPasesplasma membrane

…ATP driven cation pumps (typical),

NA+ K+

H+ K+

H+ Ca 2+ Cd2+ Hg2+ Cu2+

animals

plants, animals, fungus, yeast

animals, plants, fungus, yeast

bacteria, animals, plants, etc.

10 transporters

Plasma Membrane H+-ATPases

ATP ADP + Pi

X

2 H+

H+

Transport channels

H+ symport

H+ antiport

Plasma Membrane

2 H+

X

Proton Pump(ATPase)

H+ H+

H+

H+H+

H+

H+

300 mV

ions

Mechanisms of Transport

• Diffusion, by molecular motion,

– good only at short distances,

• Channel and Carrier mediated transport

– small molecules across membranes,

• Osmosis (water across membranes),

• Bulk Flow,

– efficient large-scale, mass movement.

Osmosis

…the diffusion of water across a selectively permeable membrane,

– water (free) moves from a region of higher H2O concentration, to a region of lower H2O concentration, until in equilibrium,

…the concentration of water is lowered by the addition of solutes.

Mechanisms of Transport

• Diffusion, by molecular motion,

– good only at short distances,

• Channel and Carrier mediated transport

– small molecules across membranes,

• Osmosis (water across membranes),

• Bulk Flow,

– efficient large-scale, mass movement.

Bulk Flow

…the concentrated movement of groups of molecules,

– in response to gravity, i.e. rain, rivers, etc.,

– in biological systems, most often in response to pressure.

r4

8

p

xVolume flow rate =

in a cylinder

viscosity ( distance

pressure gradient

viscous: tendency to resist flow

Jean Louis Marie Poiseuille (Poiseuille’s Law, ~1838)

Increase Flow?Increase radius.

Lower Viscosity.Increase Pressure.Shorten Distance.

r4

8

p

xVolume flow rate =

viscosity ( distance

pressure gradient

Friday

• Water and Water Potential,

• Cell Water Relations,

• Water Transport in Plants.

Catch up in the readings, review materials from 204 and 205 if necessary.