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Module 5 > Plant Hormones > Flashcards

Plant Hormones Flashcards

1
Q

Examples of abiotic stress

A

Freezing
Drought
Increased soil water salinity
Presence of heavy metals e.g lead, copper

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2
Q

Ways plants respond to abiotic stress
E.g response to drought?

A
  • dropping their leaves
  • shutting their stomata (so reducing water loss via transpiration)

Others:
Some plants produce an antifreeze chemical in their cells, that decreases the formation of ice crystals that can destroy plant cells if allowed to form within them

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3
Q

What is herbivory

A

Consumption of plants by herbivores

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4
Q

Chemical defences to herbivory (& folding in response to it)

A

Alkaloids
Pheeonones
Tannins

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5
Q

What are tannins

A
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6
Q

What are alkaloids

A
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7
Q

What are pheromones

A
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8
Q

What are Nastic movements

A
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9
Q

What are tropisms

A

Growth movements of a part of a plant in response to a directional stimulus

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10
Q

Postive vs negative tropism

A

Towards vs against stimulus

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11
Q

5 types of tropisms table

A
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12
Q

How did darwin investigate phototropism and show that the tip detected light

A
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13
Q

How did scientists investigate tropisms using mica to show that the growth stimulus was a chemical that could travel through gelatin

A
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14
Q

How tropism was investigated (how the tip led to curvature)

A
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15
Q

Phototropism: how they found out it was due to a hormone by replacing the tip with a block

A
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16
Q

What does auxin do

A

Control growth elongation

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17
Q

What does auxin do

A

Control growth elongation

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18
Q

Where is auxin synthesised

A

The meristems (growing tips of roots & shoots)

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19
Q

Where does auxin move after it’s synthesised in the meristems

A

Passed down the stem to stimulate elongation / growth
Then, activates proteins in cell wall (expansins) which loosen bonds between cellulose microfibrils
Therefore, flexibility increases, so more elongation

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20
Q

Phototropism mechanism pic

A
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21
Q

Negative vs positive geotropism

A

Neg = shoots grow away from gravity
(Auxin accumulates on the lower side of the shoot, therefore grows upwards) This
Pos = roots grow towards gravity
In roots = higher IAA conc, so lower rate of elongation, as IAA accumulates at the lower side, therefore inhibiting cell elongation, so the lower side grows slower, so the root bends dowm

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22
Q

Investigating geotropism

A
23
Q

What do deciduous plants do in very hot & dry conditions

A

Lose leaves to reduce water loss

24
Q

What do deciduous plants do in winter

A

Lose leaves as water absorption is difficult due to frozen soils
Leaves shedded due to photosynthesis being limited by low temperatures and reduced light

25
Q

What role does ethene play in leaf loss

A

Stimulates the breakdown of cell walls in the abscission layer, causing the leaf to drop of

26
Q

What role does auxin / IAA play in leaf loss

A

Inhibit leaf loss & are produced in young leaves, making the leaves insensitive to ethene temporarily
The conc of IAA decreases as leaves age until leaf loss can occur

27
Q

Main hormone that plays a role in stomatal closure?

A

ABA Abscisic Acid

28
Q

Examples of water stress

A

High temperature
Reduced water supplies

29
Q

What happens in times of water stress

A

ABA produced by plants to stimulate stomata closing

30
Q

How does ABA work e.g. what does it bind to etc

A
  • guard cells have ABA receptors on their cell surface membrane
    ABA binds with these receptors, inhibiting the proton pumps & therefore stopping the active transport of H+ out of guard cells
  • ABA also causes Ca2+ ions to move into the cytoplasm of the guard cells, through the cell surface membrane
31
Q

How do Ca2+ ions act as a chemical messenger to lead to stomatal closure

A
  1. Causes channel proteins to open, that allow negatively charged ions to leave the guard cells
    -> this stimulates the opening of further channel proteins that allow K+ to leave the guard cells
  2. Loss of ions = Increased W.P. Of guard cells, therefore water leaves via osmosis
    Therefore
    Guard cells become flaccid: stomata close
32
Q

Role of gibberellins

A
  • Control seed germination
  • promotes fruit development
  • promotes activity of amylase
    Can also play a role in stem elongation
33
Q

When the seed is shed from a parent plant is it active or inactive

A
  • state of dormancy (metabolically inactive): little water
    And can survive harsh weather
34
Q

What does the seed contain

A

Endosperm (a starch containing energy store)
Embryo (which grows to the new plant when the seed germinates)
Aleurone layer (outer, protein rich layer)

35
Q

What does the seed contain

A

Endosperm (a starch containing energy store)
Embryo (which grows to the new plant when the seed germinates)
Aleurone layer (outer, protein rich layer)

36
Q

H2O absorbed = germination begins.
This stimulates the embryo to produce what hormone

A

Gibberellins

37
Q

H2O absorbed = germination begins.
This stimulates the embryo to produce what hormone

A

Gibberellins

38
Q

How do gibberellins molecules lead to amylase action

A

Gibberellins diffuses into the aleurone layer & stimulates the cells to synthesise amylase

39
Q

How does amylase work to transport / give the embryo glucose

A

Amylase hydrolyses starch
Therefore soluble maltose produced
Maltose hydrolysed into glucose
Glucose transported to embryo

40
Q

What breaks dormancy of the embryo

A

When the embryo respires the glucose given after amylase action

41
Q

How does apical dominance happen

A
42
Q

Commercial uses of plant hormones

A
  • control ripening
  • fruitless seed production
  • hormone rooting powder
  • hormonal weed killers
43
Q

Other things specific hormones do
Ethene, auxin, cytokinins, gibberellins

A
44
Q

How does ethene control ripening

A
45
Q

How do auxins act as hormone root powders

A
46
Q

How do synthetic auxins act as hormonal weed killers

A
47
Q

Evidence for gibberellins role in germination and stem elongation

A
48
Q

How would you investigate diff / conc plant hormone on growth

A

Use diff hormone
Use serial dilutions

49
Q

How to investigate diff conc levels of hormone effect on plant

A
50
Q

Factors to control when investigating plant hormone action

A

Volume of water
Light intensity
Temperature
Humidity
Ideally = genetically identical plants and cuttings to ensure they response the same way

51
Q

Normal action of IAA in cells (ms answer)

A

Stimulates cell elongation & division

52
Q

How can herbicides kill plants

A

By disabling proton pumps in a photosystem
-> reducing proton pumping & therefore chemiosmosis
-> photophosphorylation stops
-> less ATP produced
-> less NADP produced
-> no Calvin cycle stage
-> no TP/hexose sugars made

53
Q
A

Module 5 (12 decks)

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