Period 1

Water movement

Printable reference generated from local Period 1 material.

LHAP 104A Botany Presentation Botany

Extracted Text and Images

Extracted locally from the source file.

Slide 1 LHAP 104: Water Relations Presentation by E. Kawahara and A. Schill http://ladymin.files.wordpress.com Slide 2 Diffusion Movement of molecules from a region of higher concentration to a region of lower concentration. Move along a diffusion gradient Move until equilibrium reached. Slide 3 Osmosis Diffusion of water through a differentially permeable membrane from a region where the water is more concentrated to a region where it is less concentrated. Slide 4 Diffusion Videos: Diffusion of Hot vs cold medium Water from high to low Water will move up the dry paper towels in order to reach equilibrium. Water moves from an area where there is a lot to an area where there is less. You can see it when the colours blend and the empty cups are filled to the same level as the original ones. Slide 5 Turgid cell vs Flaccid cell osmosis continued Slide 6 Slide 7 Water movement throughout the plant More than 90% of the water entering a plant passes into leaf air spaces and then evaporates through the stomata into the atmosphere (Transpiration). Usually less than 5% of water escapes through the cuticle. Slide 8 Xylem vessels xylem vessels are cylindrical and are connected to each other xylem vessels are dead, hollow water can move easily through xylem has lignin on its walls for strength and support Slide 9 Slide 10 Cohesion water molecules tend to stick together water molecules at the surface have a stronger bond because they don’t have as many neighbours to cohese with - this creates a “stronger hold” of the surface molecules called “surface tension” Slide 11 Adhesion Water molecules can hold to a surface other than water water molecules stick to the inside of the xylem vessels Cohesion - Tension: The more surface area to adhere to, the more the water climbs up. Slide 12 ...So that’s HOW water moves through a plant… but WHY does it move?? Slide 13 Transpirational Pull Xylem vessels are normally FULL Water evaporates out of Stomata Lower water potential is created than the adjacent cells. Creates tension on water columns, drawing water from one molecule to another, throughout the entire span of xylem cells... Slide 14 Water potential Click here to read more Slide 15 Slide 16 Slide 17 The Guard Cells... Guard Cells Photosynthesize Potassium Controls the Opening and Closing of Guard Cells. More Potassium lowers water potential. Water flows in to equalize. Guard Cell is Open. To Close it, Potassium leaves and the water follows it. Slide 18 Slide 19 What happens when the Soil doesn’t have anymore water? Guard cells must prevent transpiration (90% of water taken in is lost!) Guard cells decrease their turgor ABA (hormone) changes the water potential in the stomata

Extracted Slide Text and Images

Text and media extracted locally from the presentation.

Slide 1

LHAP 104:

Water Relations

Presentation by E. Kawahara and A. Schill

http://ladymin.files.wordpress.com

Speaker Notes

This is an area of physiology that is quickly changing -
April 20, 2018 Aarhus University published a paper suggesting that trees are not subject to a constant positive pressure, but that species vary from night to day in branch height and even girth!!
We, however; are looking at the basics of water movement in plants: How does vascular transport work in plants? And What is the effect of a water deficit in a plant?

Slide 2

Diffusion

Movement of molecules from a region of higher concentration to a region of lower concentration.

Move along a diffusion gradient

Move until equilibrium reached.

Speaker Notes

Through random motion, molecules become evenly distributed through the available space. - HOMEOSTASIS (nature seeks balance)
Diffusion gradient - movement from high to low concentration - like the Hydrogen ions in the electron transport chain during respiration.
Equilibrium - when even distribution has been reached
Rate of diffusion impacted by: air pressure, temperature (in heat, molecules have more kinetic energy), and density of medium (resistance)
Takes time - molecules are small!

Slide 3

Osmosis

Diffusion of water through a differentially permeable membrane from a region where the water is more concentrated to a region where it is less concentrated.

Speaker Notes

Solvents - liquids in which substances dissolve
Water will move so that there are equal amounts on either side of a permeable membrane OR
IT will move so that there is equal concentration.
With Osmosis - is a type of diffusion where the water moves through semi permeable membrane.
Solute cannot move, so the water moves to make both solutions equal. (hence the reason the egg gets wilty - amount of water is unequal, but diffusion of sugar is the same.)
WHAT WILL THIS EGG TASTE LIKE?

Slide 4

Diffusion Videos:

Diffusion of Hot vs cold medium

Water from high to low

Water will move up the dry paper towels in order to reach equilibrium.

Water moves from an area where there is a lot to an area where there is less.

You can see it when the colours blend and the empty cups are filled to the same level as the original ones.

Speaker Notes

With Diffusion - molecules move to establish equilibrium - equal gasses or equal mass

Slide 5

Turgid cell vs Flaccid cell

osmosis continued

Speaker Notes

Osmosis is the way water enters plants from the surroundings.
Cytoplasm is bound and cannot move out of the cell, but water is not (the Cell Wall is a SEMI permeable membrane: H2O travels into organelles like Vacuole, Mitochondria, Chloroplasts, etc)
In Cell A: Water flows in until pressure from the cell wall overcomes the solution’s ability to flow in. The vacuole is full.
In Cell B: Water has flown out (to air spaces or sacrificed for plant function). The vacuole is gone, there is no water left and the cell is weak and Flaccid.
If Cell And B were side by side, what would happen?
This is why wilt happens.
This is why plants that are under wilt do not spring back
What is the potential for a plant full of Cell Bs to seal a wound?
Some molecules are too large to simply diffuse through the cell membrane and the plant will develop protein channels that allows the molecules to move… a little bit like the ATP synthase enzyme.
THESE ARE passive transportation methods because the plant expends no energy in the process.

Slide 6

Speaker Notes

So. Plants use water for:
Turgor pressure,
Cooling (the mitochondria make heat)
Pathways to transport vital minerals
Photosynthesis -

Slide 7

Water movement throughout the plant

More than 90% of the water entering a plant passes into leaf air spaces and then evaporates through the stomata into the atmosphere (Transpiration).

Usually less than 5% of water escapes through the cuticle.

Speaker Notes

Water from soil - osmosis through cell walls of roots - heading for the Xylem.

Slide 8

Xylem vessels

xylem vessels are cylindrical and are connected to each other

xylem vessels are dead, hollow

water can move easily through

xylem has lignin on its walls for strength and support

Speaker Notes

https://en.wikipedia.org/wiki/Vessel_element
Many capillary tubes form the xylem.
Xylem is comprised of Sclerenchyma cells
They Function to transport water and minerals from the soil
Transports non organic ions such as P, amino acids, N, & hormones and chemicals
Heartwood is formed by plugging old lignified xylem tubes.
This gives woody stems the support they need to grow taller
http://www.kbg.fpv.ukf.sk/studium_materialy/morfologia_rastlin/webchap3par/3.1-7.htm - you can see xylem vessels in this cross section - they are sclerified and the lignin absorbs the dye (red) vs the thin parenchyma cell walls that are living and elastic and do not absorb the dye.

Slide 9

Speaker Notes

https://www.slideshare.net/clarot16/plant-structure-growth-development
xylem cells are designed to force water up against the pull of gravity to reach all upper parts of the plant
Note the Tracheids are the more recognizable tubes
Vessel elements are typical in ‘hardwood’ angiosperms and absent in ‘softwood’ gymnosperms… that said each species varies in density.
Vessels allow bulk flow of water
There are pits between the walls - these are made of DEAD (sclerified) cells, so they need pits to allow lateral flow
These tracheids, plates and pits need to be stopped up during CODIT
The pits also stop Cavitation (air embolisms) from spreading
Air embolisms that form destroy the water’s cohesive connection and the vessel becomes defunct. Fresh cut your flowers!!
Conifers employ torus-margo “blobs” like donut holes in a donut… Oaks, accept cavitation… maples use root pressure to avoid them.
Embolisms happen from freezing, and from drought (gasses separate from water).
There is some xylem parenchyma which can store material
5 - 10% in gymnosperms, 20-40% Angiosperms and more in tropical plants
Sapwood will hold more or less material depending on the season.
How does it force it? With Cohesive and Adhesive forces!

Slide 10

Cohesion

water molecules tend to stick together

water molecules at the surface have a stronger bond because they don’t have as many neighbours to cohese with - this creates a “stronger hold” of the surface molecules called “surface tension”

Speaker Notes

Water molecules themselves are electrically neutral BUT the asymmetrical shape means they develop some polarity.
The opposite charges attract, and there is a bond formed… This bond helps counteract gravity (like the walking water experiment)

Slide 11

Adhesion

Water molecules can hold to a surface other than water

water molecules stick to the inside of the xylem vessels

Cohesion - Tension: The more surface area to adhere to, the more the water climbs up.

Speaker Notes

Add this to Cohesion and the Water Gradient… and you have water movement.
Cohesion Tension Theory: Water molecules adhering to capillary walls, and being bound together with cohesion, create a certain amount of tension.
With Cohesion tension, the water can track up the small tubes of the xylem, countering gravity.
Imbibition -
Cellulose and Starch (found in storage tissue of cells) develop electrical charges when wet and they attract water molecules.
Water molecules adhere to larger cellulose or starch and cohese with one another… Tissues swell (alive or dead).
This is why a bowl of chickpeas or lentils will double in size when soaked. They cook much faster because they are full of water.
This is can create a huge amount of force - which is why germinating seeds or wood that has soaked in water and swollen can split rock.

Slide 12

...So that’s HOW water moves through a plant… but WHY does it move??

Speaker Notes

What are the triggers??
Transpirational Pull
Concentration gradients from the Phloem (next lecture)
Root Pressure:
In the spring especially
Also early morning (guttation) when water flows in from the soil because there are many solutes (carbs)... there’s an imbalance, which causes the inflow, which then causes extra water in the system, which allows for guttation out of hydathodes.

Slide 13

Transpirational Pull

Xylem vessels are normally FULL

Water evaporates out of Stomata

Lower water potential is created than the adjacent cells.

Creates tension on water columns, drawing water from one molecule to another, throughout the entire span of xylem cells...

Speaker Notes

Water diffuses out from the leaf surface to atmosphere via stomata and creates a low at the top of the Xylem chain, so the water travels up.
This is a water potential gradient from high in the soil to low in the roots AND THEN high in the roots to low in the stem, leaves, and atmosphere respectively.

Slide 14

Water potential

Click here to read more

Speaker Notes

We already know water wants to be in balanced quantity and concentration - this is called WATER POTENTIAL
Plasmolysis - Celery in Salt water - water potential inside the vegetable is higher than what is outside… there is MORE UNdiluted water IN the celery than there is outside, in the beaker...
Vacuoles in celery cells have disappeared and and cytoplasm is clumped in the middle, away from the walls.
(Why Soil Salinity can be a big problem - if there is enough salt in the water, it will draw water OUT of the plant and INTO the soil… potentially filling all pore spaces but not allowing the plant to take any up because the salts want to be in solution).

Slide 15

Speaker Notes

So Pure water Potential is 0. As a result, we always start at 0 Bars. Negative numbers can be confusing to look at, make sure you take your time on tests!
The trident is the symbol used to indicate water potential - psi is the 23 letter of the greek alphabet.
THE LOWER THE NUMBER, the lower the potential.
The lower the potential, THE MORE WATER WILL FLOW THERE.
We talk about water in Megapascals (MPa) because it is actually a measure of pressures - Cell Pressure, Pressure required to stop osmosis (based on solvent), etc.
Interestingly, in the spring, there is also root pressure created (more in some trees than in others) which is part of why they exude fluid SO much in the spring. The pressure tends to die down toward the summer (time your pruning).
Osmotic Pressure builds up in the roots as water flows in (to dilute concentration to sugars being converted to energy). There are no leaves yet, but this pressure is sufficient to drive up against gravity.
https://www.britannica.com/science/root-pressure

Slide 16

Speaker Notes

“A potted plant sealed under a bell jar. The surface of the soil has been covered with foil so that no water could evaporate from it. Note the accumulation of moisture on the inside of the glass. The moisture came through the plant by transpiration.” (Figure 9.9 page 152)
“More than 90% of the water that enters a plant passes through and evaporates”
An average sized birch tree can transpire from 750 - 3785 Litres / day during the growing season! And that is only 90% of what it needs.

Slide 17

The Guard Cells...

Guard Cells Photosynthesize

Potassium Controls the Opening and Closing of Guard Cells.

More Potassium lowers water potential.

Water flows in to equalize.

Guard Cell is Open.

To Close it, Potassium leaves and the water follows it.

Speaker Notes

Plants do not transport gases - only liquids. Gases must move via osmosis from cell to cell (hence the need for lenticels in wood).
In C3 plants, guard cells open when light strikes their chloroplasts (http://www.biology-pages.info/G/GasExchange.html )
Changes in turgor pressure within the cell occur when osmosis between the guard cells and other epidermal cells cause shifts in solute concentrations.
The guard cell chloroplasts have a special pump that allows Hydrogen ions out… which attracts Potassium… which in turn
An increase in potassium ions in a cell causes a lowering of the water potential and osmosis leading to turgid guard cells.(water moving in)
When photosynthesis is not occurring in the guard cells, the hydrogen concentration diminishes, potassium ions leave, and the stomata close.

Slide 18

Speaker Notes

This process also expends energy.
Where does the energy come from?

Slide 19

What happens when the Soil doesn’t have anymore water?

Guard cells must prevent transpiration (90% of water taken in is lost!)

Guard cells decrease their turgor

ABA (hormone) changes the water potential in the stomata

Speaker Notes

Abscisic acid is produced.
pH goes up.
Ions and Anions leave (Ca2+, NO3-, Cl- AND K+)
Water follows
Stomata Close
ABA also detects bacteria trying to enter and closes the stomata
Interestingly, as the concentration of CO2 rises, the number of stomata goes down (Not as much CO2 is needed maybe - but what about the Urban Heat Island - I’m surprised the number doesn’t go up due to increased cooling requirements).
(http://www.biology-pages.info/G/GasExchange.html)

Presentation

Water movement

Botany/Water movement.pptx

Presentation6.4 MB4 video links24 extracted assets

Video Links

Embedded videos found in the source file.

http://www.youtube.com/watch?v=SrON0nEEWmo

http://www.youtube.com/watch?v=A-5S2e1ubT8

http://www.youtube.com/watch?v=9EUfVIon6t8

http://www.youtube.com/watch?v=nDZud2g1RVY

Links Found

URLs discovered in the source file.