module 5 - 16.2 and 16.3 plant responses to abiotic stress and herbivory Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

which main 2 abiotic factors to plants face?

A
  • temperature fluctuations due to seasons
  • light due to fluctiations in daylight hours
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how do the seasonal changed affect rate of photosynthesis?

A
  • plants need to make enough glucose and triose phosphate from photosynthesis to meet demand of respiration and synthesis of molecules
  • plants hibernate if rate of photosynthesis is too low
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is photoprediodism?

A

plants responding to lack of light

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

what are the responses a plant does in response to lack of light?

A
  • loss of leaves
  • breaking of leaf bud dormancy
  • timing of flowering
  • tuber formation for over-wintering
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the process of abscission in plants?

A
  1. falling light levels leads to lower auxin concs
  2. leaves respond by increasing production of ethene
  3. ethene causes genes to switch on in separation layer of abscission zone, enzymes made to digest cell wall of separation layer
  4. vascular bundles in petiole are sealed off
  5. cells in protective layer of abscission zone make suberin and lignin to waterproof and protect the car when leaf falls off
  6. plant cells at abscission zone take in large amounts of water, swell, and eventually burst, making leaf fall off
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how is freezing in plants prevented?

A

molecules are produced called ‘anti-freeze’ to lower the melting point of water and prevent water freezing
- can be sugars, polysaccharides, amino acids and proteins
- produced when genes switch on due to prolonged fall in temp and reduced daylight

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

what is the mechanism for day to day stomatal opening?

A
  1. proton pump drives protons (H+) from guard cells
  2. guard cells become increasingly negative
  3. negative charge opens potassium voltage gates channels so uptake of K+ ions occurs
  4. increase in K+ conc lowers WP inside cell so water diffuses into cell by osmosis
  5. this increases cell’s volume and turgor pressure
  6. rings of cellulose microfibrils only allow extra turgor pressure to elongate guard cell causes an open pore for gas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the hormonal control of stomatal closure?

A
  1. when roots begin to sense water shortage in soil ABA is released from roots
  2. ABA binds to receptor proteins in guard cell’s membrane
  3. cause concentration of free Ca2+ to increase due to influx of guard cells
  4. causes Cl- ions to exit guard cell (chloride shift)
  5. this stops uptake of any further K+ ions into guard cells
  6. loss of K+ ions causes increased WP, so water diffuses out cell
  7. makes cell plasmolysed so stomata closes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the 4 groups of plant responses to herbivory?

A
  • physical defences
  • chemical defences
  • pheromones
  • folding on touch (mimosa pudica)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are examples of physical defences?

A

prickles, thorns, spines, stings

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

what are examples of chemical defences?

A

tannins
alkaloids
terpenoids

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

what are tannins?

A
  • have a bitter taste - puts animals off eating them
  • toxic to insects - binds to digestive enzymes & inactivates them
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are alkaloids?

A
  • bitter tasting, nitrogenous compounds found in many plants
  • act as drugs affecting metabolism of animals
  • e.g. nicotine and caffeine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are terpenoids?

A

compounds produced often form essential oils but also often act toxic to insects and fungi that might attack the plant

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

what are pheromones?

A
  • chemicals affecting social behaviour of other membranes
  • they warn other plants of herbivores and stimulating them to synthesise toxic chemicals like tannins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how does mimosa pudica fold at the touch as a defence to herbivory?

A
  • stimulus is transmitted as an electrochemical change in cells, from stimulated leaflet to leaf’s pulvinus
  • pulvini cells gain and lose turgor due to water moving in and out by osmosis
17
Q

what does an action potential cause potassium ions to do in mimosa pudica?

A

1.causes potassium ions to flow out in extensor side
2. causes potassium ions to flow into the flexor cells

18
Q

what happens to the water in mimosa pudica when it follows the ions?

A
  1. flexor cells swell and become turgid
  2. extensor cells become flaccid
    - WHOLE LEAF DROOPS