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102 Growth & Development > Lecture 4 > Flashcards

Lecture 4 Flashcards

Hormone function to co-ordinate plant development as well as responses to the environment. Genetic studies, mainly in Arabidopsis, have led to a greatly improved knowledge of genes involved in hormone perception and response

1
Q

What are phytohormones

A

regulate all stages of the plant life cycle and its defense and stress response

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2
Q

What are the 5 common phytohormones

A 
auxin
cytokinin
gibberellin
abscisic acid
ethylene
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3
Q

what are the newly discovered phytohormones

A

Brassinosteroid
salicylic acid
strigolactone
jasmonic acid

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4
Q

What is the effect of salicylic acid

A

painkiller

plant hormone

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5
Q

What is the effect of strigolactone

A

blocks axillary shoots

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6
Q

When was cytokinin discovered

A

1941

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7
Q

How was cytokinin discovered

A

demonstrated in plant culture the growth promoting properties of coconut milk

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8
Q

When did Letham and Miller purify zeatin (natural cytokinin) from Zea Mays

A

1973

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9
Q

Why is this hormone given the name cytokinin

A

for their growth promoting properties

cytokinesis = cell division

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10
Q

Where are cytokinins synthesized from

A

adenine

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11
Q

What are the natural cytokinins

A

zeatin

IPA

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12
Q

What are the synthetic cytokinins

A

Kinetin

BAP

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13
Q

What are the properties of cytokinins

A
  • promotes growth and cell division
  • delay tissue senescence
  • act antagonistically to auxin :
    promotes shoot vs root development in cultured cells.
    blocks adventitious rooting
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14
Q

true or false; cytokinins affect grain production and drought tolerance

A

true

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15
Q

What happens to rice plants that accumulate more CK

A

can produce more grain per plant because of changes in inflorescence growth

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16
Q

What happens to tobacco plants that produce more CK

A

they are more drought tolerant because of the delay of leaf senescence conferred by CK

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17
Q

What are commercial uses of CK

A

antioxidants in cut salads

release of axillary buds

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18
Q

How was ethylene discovered

A
  • noticed because of effect of gas street lights in the 1800s on adjacent plants
  • it is the first plant hormone identified
  • leaking gas caused early leaf drop
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19
Q

true or false; ethylene is a gas

A

true

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20
Q

when was ethylene discovered as an active ingredient

A

1901

21
Q

Where is ethylene derived from

A

methionine

22
Q

What are the effects of ethylene

A

a ripening hormone

23
Q

What fruits make ethylene

A

tomatoes, apples, bananas, avocado

  • make ethylene
  • ripen in response to exogenous (added) ethylene
24
Q

Why does bad apple spoil the whole bunch

A

this is because a ripening apple (or infected) gives off ethylene, which induces ripening in the surrounding apples

25
Q

What does ethylene promote

A
  • fruit ripening (promotes food softening and color development)
  • senescence
  • abscission of leaf, petals, fruit
26
Q

What does senescence mean

A

controlled process of growing old and redistribution of nutrients to growing parts of the plant

27
Q

true or false; in some cases senescence is terminated by abscission of the senescencing region

A

true

28
Q

what are snorkel genes in rice

A
  • ethylene induced elongation, so rice submerged or floating in water can produce a snorkel to keep pace with rising flood waters ( anaerobic conditions)
29
Q

How are ethylene mutants detected

A

on an agar plate all Arabidopsis seedlings are sprayed with ethylene gas. The non mutants have their growth inhibited whilst the mutant will grow tall

30
Q

Where is ethylene normally produced

A

shoot tip

  • to enable seedlings to avoid obstacles when it is germinating and growing
  • produced in response to wounding
31
Q

true or false; ethylene induces a triple response in seedlings

A

true

32
Q

What does it mean by triple response

A

as increasing amounts of ethylene are sprayed on the seedlings; they will curve, grow thicker and become shorter and shorter
- used arabidopsis mutants to work out ethylene signalling pathway

33
Q

What are the commercial uses of ethylene (adding)

A
  • ripening stimulation (tomatoes, bananas)

- induction of abscission prior to mechanical harvest (cherries)

34
Q

commercial uses of ethylene (blocking or removing it)

A
  • removal of ethylene gas (scrubbing) during apple storage (to halt ripening and spoilage)
  • treatment of cut flowers with silver ions (block ethylene perception) to stay fresh longer
35
Q

Who discovered Gibberellin and when

A

Kurosawa
1926
“foolish seedling disease”

36
Q

How was Gibberellin discovered

A

compound secreted by fungus Gibberella fujikuroi

  • in rice caused excessive shoot elongation, grain poor or absent
  • named Gibberellin after the fungus
37
Q

true or false; there are 80 natural GA molecules made from mevalonate pathway

A

true

38
Q

What is the classic role of Gibberellin (GA)

A

Hyper elongation of shoots by stimulation of both cell division and cell elongation (tall plants)

  • seed germination
  • stimulation of flowering in long day and biennial plants
  • fruit development
39
Q

What initiated the Green Revolution of the 20th century

  • genes controlling GA synthesis
  • due to GA mutants
A

due to increased use of fertilizer and introduction of semi dwarf varieties of gran
- semi dwarf varieties put more energy into seed production than stem growth and are sturdier and less likely to fall over

40
Q

What are commercial uses of GA

A
  • parthenocarpic development of fruit gives seedless table grapes
41
Q

What does parthenocarpy mean

A

fruit development in the absence of seeds

42
Q

What are the properties of ABA (abscisic acid)

A

found in:

  • dormant seeds (dried out)
  • buds and water stressed tissues such as mature leaves

effects:
not involved in abscission

43
Q

Where is ABA made from

A

mevalonate pathway

44
Q

What are the major roles of ABA

A

protect the plant from water stress

induces stomatal closure (reduces transpiration and water loss)

45
Q

what is the ‘ein’ mutant

A

an ethylene insensitive mutant

- fails to undergo triple response in the presence of ethylene

46
Q

What is the ‘ctr’ mutant

A

a constitutive triple response mutant

- undergoes the triple response even in the absence of ethylene

47
Q

What is the effect of GA3 on the growth of Thomson seedless grapes

A

looser cluster of larger grapes

48
Q

What are Brassinosteroids

A

are steroid molecules similar to cholesterol

and to animal hormones; purified from rapeseed

49
Q

What is brassinosteroid required for

A
  • required for normal plant development

- stimulate cell division and elongation

102 Growth & Development (10 decks)

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