module 5 - 16.1 plant hormones and growth in plants Flashcards

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1
Q

what is a tropism?

A

involves differential growth of plant cells triggered by chemical messages produced in response to particular stimuli

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2
Q

what is an abiotic factor?

A

non-living components of a habitat

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3
Q

what is a biotic factor?

A

living components of an ecosystem

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4
Q

what does dicotyledonous mean?

A

plants producing seeds containing 2 cotyledons which act as food stores for developing embryos and form first leaves when seed germinates

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5
Q

what does monocotyledonous mean?

A

plants producing seeds containing 1 cotyledon which act as food stores for developing embryos and form first leaves when seed germinates

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6
Q

what are the main hormones a plant produced?

A

auxins
gibberellins
ethene
abscisic acid (ABA)

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7
Q

what is the sequence of seed germination?

A
  1. seed absorbs water
  2. enzymes produced (proteases, amylase, maltase)
  3. products of digestion used to generate ATP and act as monomers for new macromolecules
  4. gibberellins switch on genes in the embryo that code for these enzymes
  5. ABA acts as antagonist to gibberellins to prevent early germination
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8
Q

how does ABA act as an antagonist?

A

high levels of ABA stops gibberellins switching genes on for early germination

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9
Q

what is the relationship between gibberellins and ABA?

A
  • inverse relationship
  • suggests there is a regulation look that establishes balance of gibberellin and ABA
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10
Q

how are mutant seeds evidence for gibberellin and germination?

A
  • mutant varieties of seeds have non-working alleles that allow for gibberellin synthesis
  • mutants cannot produce giberellins
  • mutants cannot germinate
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11
Q

how are gibberellin biosynthesis inhibitors evidence for giberelling and germination?

A
  • when gibberellin synthesis inhibitors are applies to seeds the seeds cannot make gibberellins
  • treated seeds do not germinate
  • when either inhibitor is removes or gibberellins are applied, seeds then germinate
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12
Q

what are meristems?

A
  • tissue in most plants containing undifferentiated cells
  • found in zones of plant where growth occurs
  • give rise to various organs of the plant and keep plant growing
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13
Q

what are the 3 types of meristems?

A

apical - tips, root and shoot
intercalary - middle, only in monocot stems at base of nodes, and leaf blades
lateral - at the sides

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14
Q

what are auxins?

A
  • made in apical meristems
  • translocated in phloem, mainly from shoot tip to root tip
  • stimulate growth of main apical shoot
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15
Q

how do auxins stimulate growth of main apical shoot?

A
  • bind to receptors in cell membrane
  • causes fall in cellular pH to pH5
  • optimum pH for enzymes that keep cell walls flexible
  • cells mature and move aware from the meristem, auxins also destroyed
  • pH rises and inhibits enzymes that were keeping cell wall flexible
  • cell wall now becomes inflexible and rigid, cell size is fixed
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16
Q

what is the main auxin?

A

IAA - indoleacetic acid

17
Q

what is apical dominance?

A

when high concentrations of auxin suppress lateral shoots

18
Q

what do high concentrations of auxin do?

A

inhibit lateral shoot growth

19
Q

what do lower concentrations of auxin do?

A

allow lateral shoot growth

20
Q

what is the experimental evidence for apical dominance?

A

if auxin is applied to a cut surface, from apical meristem, then apical dominance is restored and lateral shoot growth is repressed

21
Q

what concentration of auxins promote root growth?

A

lower concentrations

22
Q

how does lower concentrations of auxin promote root growth?

A
  • auxins are produced in the root meristem
  • auxin reaches root by translocation through phloem from shoot meristem
  • auxins promote root initiation
  • high concs of auxins inhibit root elongation and enhance branching root formation
23
Q

what is the experimental evidence for lower concentrations of auxin promoting root growth?

A

replacing auxins at the cut apical stem restores root elongation and growth

24
Q

what is the role of gibberellins?

A
  • control internode length
  • excess concs of gibberellins produce tall spindle plants with large internodes
25
Q

what are internodes?

A

length between leaves or nodes on a stem