Properties of Water
What are the three properties of water?
Cohesion
Adhesion
Surface Tension
Water potential is what?
The potential in a particular solution.
- Water is going to flow from areas of high potential to low potential.
What are the three pathways of movement through a plant?
- Apoplastic
- Symplastic
- Transmembrane
What is Transpiration?
Loss of water vapor from above ground parts of the plant
What is translocation? There are two things associated with translocation, what are they?
Translocation: movement of photosynthesis (sugars) through the plant
- Sources: making the food
- Sinks: places that need food but not producing it
What is Cohesion?
Cohesion: binding of water to itself - hydrogen bonding
What two factors must be taken into account when talking about water potential?
Bonus: Why will one of these factors never be 0 in a cell?
Solute Potential
Pressure Potential
Bonus:
Solute potential will never be 0 because a cell is always going to have some solutes present. A 0 means that the cell only has pure water present. - 100 pts
What is the symplastic route?
Symplastic Route: water moving through plasmodesmata
How do plants replace the water that they've lost?
They pull water from their roots, it travels through the xylem
Why would the xylem be situated right next to the phloem? What good does that do the plant?
The phloem is able to use some of the water from the xylem to kind of distill the photosynthetic material (sugars). The sugars are too thick to force it to move on its own, so water is added to the sugars to help with movement.
What is Adhesion?
Adhesion: binding of water molecules and another molecule
What does it mean for something to have a low solute potential? How is water going to move when talking about solute potential?
- To have a low solute potential means a high concentration of solutes in a solution.
- Water moves through osmosis for solute potential
What is the apoplastic route?
Apoplastic Route: movement of water through cell walls
How does water enter the plant?
Bonus: When the concentration of water outside = inside of the plant. What must happen?
Water enters the plant through the manipulation of solute potential in the roots.
Bonus:
The plant has to switch from using solute potential to pull water in and instead use pressure potential. - 100 pts
How is the plant able to move large amounts of sugars (which are hard to move)?
A glucose-sucrose cotransporter is used. They're going to create a difference with the H+ ions, which makes a concentration gradient that ca push the sugar out of the cell.
What is surface tension?
Surface Tension: water resists any force that increases its surface area
High pressure potential means what for the water?
High pressure potential means that the water wants to leave. More pressure applied to the water means that the water wants to escape. Think about it, have you ever seen water get compressed? It will get compressed to a certain point before it fights back and breaks the containment.
What does the transmembrane route do?
Transmembrane Route: water travels through cell walls and membranes
- moving through living cells
Why can't the xylem take up water?
The xylem is dead, it has no control over the solute pressure, or anything that travels through it. Thats why its so important that other cells can filter the water to prevent toxic ions/nutrients the plant wants to keep into the xylem.
Why can the plant not DIRECTLY move the sugars?
To move the sugars it would require a LOT more ATP than the cell could expend for just moving sugars. It would also take more ATP to move the sugars than it would take the cell to make a H+ gradient and just have the sugars move through solute potential.
Why is it important that water moves from a high concentration/potential to low concentration/potential?
Water wants to move to a lower potential so it can move more freely. More space = more wiggle room for the water. Pure water (at atmospheric pressure) has the water potential of 0.
Why would a cell NOT want to have low solute potential and low pressure potential?
Having both of these things means that the cell is likely to burst with an influx of water. Low solute potential = lots of solutes, because of this the water wants in, but also low pressure potential. If the outside of the cell is experiencing a higher pressure potential, then the water is really going to want to get into the cell.
What cuts off the apoplastic route? Why can the water not continue through this route, why does the plant prevent it?
Bonus: Which kind of fungi have more of an interference with the Casparian strip? Why is this fungi interrupted by the Casparian strip?
The Casparian strip cuts off the apoplastic route. Its cut off to prevent unfiltered water from getting into the cells. Unfiltered water could lead to disease, uptake of something the plant doesn't want, or mean the plant hasn't pulled the nutrients it needs out of it.
Bonus:
Arbuscular. This is because the arbuscular is actually interacts with the cell membrane of the plant cell. Because of this the casparian strip interferes more/interupts the function/relationship between the fungi and plant - 200 points
How can plants not expend energy on the transportation of water? Why is it important that the plants do this?
Plants don't expend energy because xylem is able to be used as a straw. Because it is hollow, as soon as the water evaporates or leaves through the leaf, the xylem is able to pull more water out and up the tree/plant. - No expenditure of energy as all the water is ONE chain. Its important that plants DO NOT expend energy on this because if they did, they'd be wasting too much energy.
In the Pressure-Flow Hypothesis, how does the companion cell help?
Bonus: Why will the plant need to move the photosynthetic material to the sink cells? Why can sink cells not rely on the sugars that they produce?
Companion cells in phloem are going to push sugar into sieve tube elements to lower the solute potential. The excess sugar production is going to be shunted through the companion cell to sieve tube.
- Low solute potential in sieve tube draws water over from xylem and helps with the flow of the photosynthetic materials.
Bonus:
Plant needs to move photosynthetic material so it doesn't clog up the parenchyma cells, which would slow down photosynthesis.
Sink cells DO NOT make their own sugars, that's why they rely on the photosynthetic material of the plant to provide them with sugars. (Most of the time the sink cells have high metabolic rates or could be used for storage.) 200 pts