Theme 4 Homeostasis In Land Plants Part 4 Flashcards

1
Q

What do endodermal cells acts as

A

A selective barrier

The ions are actively transported into the xylem (using energy)

Active because already lots of nitrate on inside but want more from outside

Less to more so active (against gradient)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Movement of water is controlled by

A

Osmosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

In the symplastic pathway what does the water go through

A

The vacuools or the cell cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the casparian strip

A

It’s in the roots endodermis

It forces the apoplastic water and dissolved minerals into the symplast and into the endodermis

Makes sure all solutes and water enter the xylem (vasculature) which then lets the plant regulate the ions passing into the vascular tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does the casparian strip do once solutes have passed through the xylem

A

Restricts them from flowing back out because of gravity

Leaves whatever plant doesn’t need in the roots

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does the water go to the top of the trees (travel up the xylem) once inside

A

Transpiration
Cohesion-tension mechanism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does transpiration due to the leaf anatomy help water move up the xylem

A

The leaves have many stomatal Pores and large air space

The air space gives area for evaporation to happen

The small xylem veins a very close to the stomatal openings and they dump water into the stomatal pores (the water potential in leaves is lower)

A negative tension is made by evaporation and water gets pulled up from xylem and out of the pores and then the next water molecule comes up

90% of the water is lost through this

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the cohesion tension mechanism of transport

A

It’s driven by transpiration

There’s cohesion between water molecules (h bonds)

There’s adhesion between the xylem and the water because of the interaction with cellulose in the xylem this adds tension

So when water is evaporated the next and next and next water molecules get pulled upward while attached to the xylem

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does the column resist the negative pressure due to transpiration and negative tension

A

To stop from collapsing due to tension, the secondary cell wall of lignin,
the adhesive forces in the xylem (with h20)
and the weight of the column help

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is root pressure

A

Positive (upward) pressure in roots that pulls forces xylem sap upward

Happens in high humidity or low light

Cal only Move water up very short distances since transpiration is slower in high humidity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is guttation

A

Occurs due to root pressure

In high humidity or low light

Water is pushed out of xylem and left on the edges of plants

Only in small plants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What conditions increase transpiration

A

Hot, dry, and windy conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How do plants prevent drying out (excessive water loss) due to transpiration

A

If hot conditions the plant wants to conserve water

the stomata is closed by the guard cells

But closing it off slows down photosynthesis and causes overheating

This is the trade off to conserve water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

If it’s humid conditions what happens to the stomata

A

Stomatal open

But since so much water outside already cause of humidity the transpiration will be low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Xylem moves what

A

Just water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

If something is talking about bulk flow, pressure flow, movement of organics, sieve tube what it it related to

A

The phloem

17
Q

What is translocation

How is it diff from the xylem

A

Long distance transport of substances through the phloem

It’s multi directional transport depending on where the pressure is (xylem xylem is unidirectional)

18
Q

Is xylem hydrophobic or hydrophilic

A

Hydrophobic

19
Q

What is phloem sap

A

Water and organic compounds

Not just sugar, has amino acids, organic acids, organic nitrogen compounds, hormone, and other signal molecules

They flow through the sieve tube

20
Q

What drives the flow of phloem sap

A

The difference in pressure between the source and the sink regions

21
Q

What is the source

A

Any area of the plant where organic stuff is loaded into the phloem

Place where food is made

22
Q

What is the sink

A

Any area of the plant where organic stuff is unloaded from phloem

Place where food is stored

23
Q

What is the sink in winter
What is the sink in spring

A

The roots
The mature leaves

24
Q

What is the source in winter
What is the source in spring

A

The leaves
The roots

25
What is the phloem composed of
Sieve tubes and companion cells Each dive tube has its own companion cell with a plasmodesmata in between They’re alive at maturity
26
What do sieve tubes do as they mature
To get more area for flow of phloem sap, they lose their nucleus, vacuoles and organelles This is done by partial programmed cell death
27
What happens in partial programmed cell death
The phloem mother cell undergoes asymmetric cell division to give the sieve element and companion cell The sieve element has no space to transport nutrients so it’s does ppcd and loses its vacuole/tonoplast, ribosomes, nucleus, Golgi body, and cytoskeleton All it’s left with after are the plasma membrane, plastids, mitochondria, the endoplasmic reticulum It’s still alive because the companian cell has all of the things the sieve element is missing Sieve plates are formed that connect the sieve element and companian cell The remaining organelles line to the walls of the sieve tube P-proteins are also there to fix breakage of the tube Then the tube is ready to transport
28
What are sieve plates
Modified cell walls with plasma membrane lined pores
29
What are the two mechanism of sugar loading
Apoplastic and symplastic Same as xylem
30
Sealing up break in the phloem IDK
Idk
31
What is similar in the xylem and phloem about sugar and water loading
They both have to cross the plasma membrane They have to get into symplastic route to be transported
32
Unloading of sugars is
Symplastic
33
What is the process of sucrose being loading into the phloem at a source (leaves) What happens to the water potential
It is actively loaded into the phloem (eventually gets to sieve tubes) The photosynthetic cell accumulates simple sugars : glucose fructose and galactose These get transported through the smaller plasmodesmata into the companion cell The sugars are made larger in the companian cell and turn into sucrose raffinose and stachyose These larger sugars go though the larger plasmodesmata connection and into the sieve tube The more sucrose loaded into the sieve tubes, the lower the water potential
34
Why do are the plasmodesmata connecting the photosynthetic cell and the companian cell smaller than the other ones
Since the sugars get converted to larger sugars, they can only go through to the sieve tube with the bigger opening To prevent from sugars going back into the photosynthetic cell
35
What do pressure flow mechanisms do in relation to the phloem
Moves substances by bulls flow under pressure from sources to sinks based on water potential gradients Loading from the source then Transported to sieve tube then unloaded into sinks
36
What is the water potential in the sieve tubes What about in the xylem So which way does water move Then what happens
Lower Higher From the xylem to the phloem, creates more turgor pressure in sieve tubes at the top The sap in the phloem travels IN BULK to the sink (roots) cause lower pressure there Sucrose is unloaded to sink cells Then water flows back to the xylem though osmosis the lower it gets in the sieve tube since water potential gets higher there