Diffusion, Osmosis, and Active Transport

Short-Distance Intercellular Transport

The Water Available in Water

Long-Distance Transport: Xylem

Water Potential

Long-Distance Transport: Phloem

The Water Available in Air

Transfer Cells

Motor Cells

Guard Cells

Material transferred from cell to cell across membrane

apoplast

symplast

Active Transport

cells interconnected by plasmodesmata

Diffusion

diff regions get diff amounts water

air pulls water out of plants

variety of forms

air supplies water to land plants

timing & regularity of precipitation important

eutrophication

water starts out as rain

ocean water

sources

sinks

water at top mountains pure

Water Transport Through Xylem

Properties of Water

pressure flow hypothesis

Control of Water Transport by Guard Cells

three components

free energy of water

Cells and Water Movement

water moves from positive to negative regions

measured in megapascals

pressure

similar to guard cells

plasma membrane

larger membrane

found in areas w/rapid short-distance transport

examples

move slowly and reorient themselves

desert none/little precipitation

fog & cloud regions

night

day

osmosis

molecular pumps

small molecules move through wall and intercellular spaces

glandular regions

fusion between transport vesicles & plasma membrane

all of the protoplasm of one plant

nonglandular regions

one continuous mass

algae die

fresh

molecular pumps

examples

motive force for transpiration

fine cytoplasmic channels

less pure as it collects

too much salt

salty

particles move high to low

brackish

frost

very pure

rain

snow

through a membranne

dew

sugars actively unloaded from sieve elements into surrounding cells

fog

hail

humidity

receive transported phloem sap

pressure potential

not all active simultaneously

rate water lost

movement influenced by powered by water loss in atmosphere

osmotic potential

pressure potential

water heavy

little internal pressure

guard cells close

shrunken

active transport

membrane bound molecular pumps

osmotic potential

bodies decomposed by bacteria

uses up so much oxygen

can't grow w/out phosphate

mostly cell wall :

mc absorbed

sugars actively transported

sites where nutrients are transported

intercellular space

extremely diverse

phloem loading

respiration

protein

proton pumping photosynthesis

cohesion tension hypothesis

cavitation

water loss through cuticle

most powerful mechanism

MPa

heavy

cells grow not burst

use ATP to force molecules across membrane

matric potential

moves when diff in water potential in cell

decreased

bars

negative

algae can't live here

finger-like/ ridge-like outgrowths inner surface

light most often controls guard cells water relations

potentials always in pairs/groups

water always in air

positive

can accumulate or expel K+

capacity to do work decreased

location of flexture

movement based on simple properties & solutions

osmotic potential less neg

Prayer Plant

guard cells open

more molecular pumps

pressed firmly against all convolutions

water potential less neg

plants don't all produce organs @ same time

change enormously

flex and fold in response to stimulus

distelled

increased

equal in two regions

cannot use to hydrate

tension on mc (pull)

effect of pressure on water potential

intracellular transport

process reversed

outer surface area of walls smooth

hydrophobic molecules

pass through primary cell walls

fruits can only develop after flowers

hydrophyilic molecules

sieve elements

storage sites

Venus Flytrap

ATP splits into ADP & phosphate

kills fish

effect solutes have on water potential

open stomatal pores allow water loss

water mc must lift weight of entire water column

Osmosis

breaks hydrogen bonds

sieve cells

other plants

hydraulic equilibrium w/surrounding cells

exception in CAM plants

triggered by water stress

along numerous vascular bundles

does not increase or decrease more than a few megapascals

loss of sugar

phloem sap more dilute

sigh pie

water loss still problem

leaves dehydrate

= 10 bars

lifting to top of tree requires a lot of energy

often occurs in early afternoon

leaves dominant

cool

adjust water potential & turgidity

number of particles present in solution

mc move easily

pressure potential neg #

tracheid or vessel can never conduct water again

where petiole attaches to lamina or stem

water molecules interact w/ other substances

K+ ions actively transported

blue light

early spring

water molecules interact strongly w/one another

lowering it

something compressed

entire midrib

decrease pressure

K+ pumped from guard cells -> surrounding cells

membrane extremely impermeable

energy transported to pump

water under pressure decreases

something stretched

much larger surface area than flat

adheres to substance

heat

diffuse easily through any membrane

elevation

sugar accumulation causes concentration

equalibrium

binds to molecule & ATP

no net movement of water

increase pressure

pure water

photosynthetic fixing of CO2

polar

plants other than angiosperms

water diffuses outward

phloem loaded by polymer trap mechanism

water under pressure increases

significant when stomatal pores open

adding soultes

transstomatal transpiration

apoplastic space

completely impermeable

doesn't break cells

incipient plasmolysis

vesicles migrate through cytoplasm and fuse with organelle

freely permeable

release abscisic acid

pressure builds

no net change occurs

differentially permeable membranes

inner bark in storage roots & stems

network bundles in tublers & corms

cohesion overcome

massive loading

warm, dry days

spring

summer

water's adhesion to dissolved structures

K+ cannot leave once inside

diffusion not possible

guard cells close stomatal pore

fine veins in leaves

surrounding cells -> guard cells

water enters & leaves same rate

differentially/selectively permeable

adhesive

cells @ joints

cohesive

triggerswavelength

STM/CC complex

membranes permeable to mono & disaccharides

simple sugars diffuse into conducting cells

hydraulic disequalibrium

water follows

equilibrium

open means trade off

osmotic potential more neg

water potential more neg

water potetial decreasses

hydrophobic

epidermal & mesophyll cells lose water

palisade parenchyma

some water lost through cuticle

filled w/ moisture saturated air

spongy mesophyll

decrease in internal carbon may lead to openings

vesicle contents transferred

pressure potential decreases

only if has aqauporins

isolation barriers

no solutes

water potential increases

all solutes

impermeable plasma membrane

not reached equilibrium

decreases water free energy

nothing passes through

little biological significance

quite important

protoplast loses just enough water to pull slightly from walls

mass transfer

large volume of material flows from source

membranes merge

pressure potential increases

water column breaks

end cells do not swell

soil particles

phloem sap flow rapidly into sink

only decreases water's free energy

only certain substances

hydrogen bonding broken

water adheres firmly to soil particles

almost all substances

hormone

cell walls

membranes

lipid/protein membrane

lipids don't interact w/water

polymerized into polysaccharides

potentials more neg

transcuticular transpiration

protoplasm squeezed

CO2 absorption

presure builds,

H2O water loss

little water passes through

protoplast pulls away completely & shrinks

osmotic potential negative

nutrients/sugars transported by phloem per hour

dry soil

specific mass transfer

phloem sap under pressure

matric potential always negative

acts as broken cable

membrane disintegrates

water not absorbed easily

danger uncontrolled bleeding

mc above cavitation point

osmotic potential 0.0MPa

vacuolar creates phloem sap

two mechanisms seal sieve elements

drawn rapidly upward

P-protein

callose

free of water weight below them

fine network

pressure drop

not in conifers

in all eudicots

stays in solution only under pressure

phloem ruptured, P-protein swept in cell center

protein channels

if cut

advantageous in wet soil

mc below cavitation point

not in all monocots

adjacent to plasma membrane of uninjured sieve elements

moist soil

between points

cell plasmolyzed

tangled mess

callose precipitates into floccurent mass

to large to pass through

embolism

roots absorb free liquid H2O

water carries mineral from roots to shoots

rush downward

forms P-protein plug

carried w/P-protein to sieve areas

callose contributes to plug

air bubble

expands till surface encounters solid barrier

transpiration occurs

leaking prevented

no support

pit membrane

prevent heat stress

if dry, potential lethal threat