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AP Biology Semester 2 > Chapter 39 > Flashcards

Chapter 39 Flashcards

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1
Q

etiolation

A

morphological adaptions for growing in darkness

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2
Q

de-etiolation

A

when plants that were growing in darkness now are exposed to light and their shoots and roots grow normally

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3
Q

what are the steps to signal-transduction pathways

A
  1. reception
  2. transduction
  3. response
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4
Q

what happens in the reception part of transduction pathways

A

Internal and external signals are detected by receptors, proteins that change in response to specific stimuli
• In de-etiolation, the receptor is a phytochrome capable of detecting light

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5
Q

second messengers

A

molecules that transfer and amplify signals from receptors to proteins that cause responses

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6
Q

what are the two types of second messengers in plants?

A
  1. Ca2+ ions

2. cGMP

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7
Q

how does the phytochrome receptor work?

A

– Opening Ca2+ channels, which increases Ca2+

levels in the cytosol – Activating an enzyme that produces cGMP

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8
Q

what happens in transduction

A

second messengers send a message to kinases to do something

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9
Q

what happens in “resonse” section of transduction pathway?

A

-regulation of one or more cellular activities
-activate transcription factors
-activate enzymes in cytosol
-

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10
Q

what is post-translational modification?

A

modification of existing proteins in the signal response

  • often involves phosphorylation of specific amino acids
  • cGMP and Ca2+ activate protein kinases directly
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11
Q

De- etiolation activates enzymes that do what?

A
  1. function in photosynthesis directly
  2. supply the chemical precursors for chlorophyll production
  3. affect the levels of plant hormones that regulate growth
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12
Q

hormones

A

chemical signals that modify or control one or more specific physiological processes within a plant

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13
Q

tropism

A

any response resulting in curvature of organs toward or away from a stimulus

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14
Q

phototropism

A
  • a plant’s response to light
  • They observed that a grass seedling could bend toward light only if the tip of the coleoptile was present
  • They postulated that a signal was transmitted from the tip to the elongating region
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15
Q

auxin hormone

A

-a chemical that promotes elongation of the pointed protective sheath covering the emerging shoot
- produced in the shoot tips and is transported down the stem
-• According to the acid growth hypothesis, auxin stimulates proton pumps in the plasma membrane
• The proton pumps lower the pH in the cell wall, activating expansins (that loosen the wall’s fabric)
• With the cellulose loosened, the cell can elongate
-also alters gene expression and stimulates a sustained growth response

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16
Q

expansins

A

enzymes that loosen the wall’s fabric

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17
Q

if auxin is reduced in the shoot what happens?

A

the lower branches begin to show growth

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18
Q

the activity of the vascular cambium is under the control of what?

A

auxin transport

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19
Q

cytokinins

A
  • stimulate cytokinesis (cell division)
  • produced in actively growing tissues such as roots, embryos, and fruites
  • cytokinins work together with auxin to control cell division and differentiation
  • if auxin is not present cytokinin can take control and help lower branches grow
  • slow aging of some plant organs by inhibiting protein breakdown, stimulation RNA and protein synthesis, and mobilizing nutrients from surrounding tissues
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20
Q

gibberellins

A
  • stem elongation, fruit growth, and seed germination
  • produced in young roots and leaves
  • stimulate growth of leaves and stems
  • stimulate cell elongation and cell division
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21
Q

brassinosteroids

A
  • similar to sex hormones of animals
  • induce cell elongation and division in stem segments
  • slow leaf abscission and promote xylem differentiation
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22
Q

abscisic acid

A
  • slows growth
  • seed dormancy ; ensures that the seed will germinate only in optimal conditions
  • dormancy is broken when ABA is removed by heavy rain, light or prolonged cold
  • early germination can be caused by inactive or low levels of ABA
  • drought tolerance; the primary internal signal that enables plants to withstand drought
  • ABA accumulation causes stomata to close rapidly
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23
Q

strigolactones

A
  • stimulate seed germination
  • help est. mychorrhizal associations
  • help control apical dominance
  • striga seeds germinate when host plants exude strigolactones through their roots
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24
Q

ethylene

A

a response to stresses such as drought, flooding, mechanical pressure injury, and infection
-effects of ethylene include response to mechanical stress, senescence, leaf abscission, and fruit ripening

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25
Q

what is the triple response?

A
  • something that allows a growing shoot to avoid obstacles

- it consists of a slowing of stem elongation, a thickening of the stem, and horizontal growth

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26
Q

senescence

A

the programmed death of cells of organs

- the process of aging in plants

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27
Q

leaf abscission

A
  • a change in the balance of auxin and ethylene controls leaf abscission, the process that occurs in autumn when a leaf falls
  • when plants drop their leaves
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28
Q

what triggers the rippening process in a fruit?

A

a burst of ethylene

-then ripening triggers release of more ethylene

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29
Q

photomorphogenesis

A

effects of light on plant morphology

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30
Q

action spectrum

A

a graph that depicts relative response of a process to different wavelengths

31
Q

what are the two major classes of light receptors?

A
  1. blue-light photoreceptors

2. phytochromes

32
Q

blue light photoreceptors

A

• Various blue-light photoreceptors control hypocotyl elongation, stomatal opening, and phototropism

33
Q

phytochromes

A

• Phytochromes are pigments that regulate many
of a plant’s responses to light throughout its life
• These responses include seed germination and shade avoidance

34
Q

many seeds remain dormant until what?

A

light conditions change

35
Q

what type of light increases germination?

A

red light

36
Q

what type of light inhibits germination?

A

far - red light

37
Q

germination

A

the process by which a plant grows from a seed.

38
Q

the photoreceptor responsible for the opposing effects of red and far-red light is a _____

A

phytochrome

39
Q

phytochromes exist in what two states?

A

P “r” and P “fr”

  • P “r” is the phytochrome shape that accepts red light
  • P “fr” is the phytochrome shape that accepts far red light
  • P “r” that gets red light changes to a P “fr” shape
  • P “fr” that gets far red light changes to a P “r” shape
40
Q

if the cytochrome is hit with red light then what happens?

A

the cytochrome changes shape to far red light cytochrome and germination occurs

41
Q

if the cytochrome is hit with far red light then what happens?

A

the cytochrome changes shape to red light cytochrome and germination is inhibited and nothing occurs

42
Q

circadian rhythms

A

cycles that are about 24 hours long and are governed by an internal “clock”
-clock depends on synthesis of a protein regulated through feedback control and may be common to all eukaryotes

43
Q

photoperiod

A

the relative lengths of night and day, is the environmental stimulus plants use
most often to detect the time of year

44
Q

photoperiodism

A

physiological response to photoperiod

45
Q

short day plants

A

plants that flower when a light period is shorter than a critical length (of darkness)

46
Q

long day plants

A

plants that flower when a light period is longer (if it passes the critical length of darkness)

47
Q

day neutral plants

A

controlled by plant maturity

-not photperiod

48
Q

is photoperiod controlled by night length or by day length

A

night length

49
Q

after how long of the photoperiod do plants flower?

A

-Some plants flower after only a single exposure to the required photoperiod
• Other plants need several successive days of the required photoperiod

50
Q

photoperiod is detected by what part of the plants?

A

by leaves (which cue buds to develop as flowers)

51
Q

florigen

A

the flowering signal (when buds are cued to develop as flowers)

52
Q

short day /long night plants have their flowers bloom only when…

A
  • they spent atleast the minimal amount of hours (according to critical dark period) in dark
  • continuous dark hours in dark as well
53
Q

long day/short night plants have their flowers bloom only when….

A
  • when hours in darkness are less than the critical dark period
  • when the hours in darkness (if over the critical dark period) is interrupted by a red light
54
Q

gravitropism

A

response to gravity

-roots show positive gravitropism; shoots show negative gravitropism

55
Q

thigmomorphogenesis

A

changes in form that result from mechanical disturbance

56
Q

thigmotropism

A

growth in response to touch

-occurs in vines and other climbing plants

57
Q

action potentials

A

-rapid leaf movements in response to mechanical stimulation are examples of transmission of electrical impulses

58
Q

abiotic stresses

A

nonliving stresses

-ex) drought, flooding, salt stress, heat stress, and cold stress

59
Q

biotic stresses

A

living stresses

-ex) herbivores and pathogens

60
Q

what happens to plants during drought

A
  • plants reduce transpiration by closing stomata, slowing leaf growth, and reducing exposed surface area
  • Growth of shallow roots is inhibited, while deeper roots continue to grow
61
Q

what happens to plants during flooding

A

Enzymatic destruction of root cortex cells creates air tubes that help plants survive oxygen deprivation during flooding

62
Q

what happens to plants with salt stress

A

Salt can lower the water potential of the soil solution and reduce water uptake
• Plants respond to salt stress by producing solutes tolerated at high concentrations
• This process keeps the water potential of cells more negative than that of the soil solution

63
Q

what happens to plants during heat stress

A

Excessive heat can denature a plant’s

enzymes

64
Q

heat shock proteins

A

help protect other proteins from heat stress

65
Q

what happens to plants under cold stress?

A

Cold temperatures decrease membrane fluidity
• Altering lipid composition of membranes is a response to cold stress
• Freezing causes ice to form in a plant’s cell walls
and intercellular spaces
• Many plants, as well as other organisms, have antifreeze proteins that prevent ice crystals from growing and damaging cells

66
Q

what do plants do to fight of living stresses like herbivores?

A

Plants counter excessive herbivory with physical defenses, such as thorns and trichomes, and chemical defenses, such as distasteful or toxic compounds
• Some plants even “recruit” predatory animals
that help defend against specific herbivores
-Plants damaged by insects can release volatile chemicals to warn other plants of the same species

67
Q

what do plants do to protect against pathogens

A

-A plant’s first line of defense against infection is
the barrier presented by the epidermis and periderm
• If a pathogen penetrates the dermal tissue, the second line of defense is a chemical attack that kills the pathogen and prevents its spread
• This second defense system is enhanced by the inherited ability to recognize certain pathogens

68
Q

virulent pathogen

A

one that a plant has little specific defense against

69
Q

avirulent pathogen

A

one that may harm but does not kill the host plant

70
Q

gene for gene recognition

A

recognition of elicitor molecules by the protein products of specific plant disease resistance (R) genes

71
Q

what is the hypersensitive response

A

– Causes cell and tissue death near the infection site
– Induces production of phytoalexins and PR proteins, which attack the pathogen
– Stimulates changes in the cell wall that confine the pathogen

72
Q

systemic acquired resistance

A

causes systemic expression of defense genes and is a long-lasting response

73
Q

salicylic acid

A

ynthesized around the infection site and is likely the signal that triggers systemic acquired resistance

AP Biology Semester 2 (5 decks)

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