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Plant Physiology > Flowers, Fruits, and Seeds > Flashcards

Flowers, Fruits, and Seeds Flashcards

1
Q

how can floral meristems be distinguished from vegetative meristems?

A

by their large size

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2
Q

what is the transition to reproductive development marked by?

A

an increase in the frequency of cell divisions in the central zone of the shoot apical meristem

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3
Q

primary inflorescence meristem

A
  • when reproduction is initiated, the vegetative meristem is transformed in the primary inflorescence meristem
  • bears cauline leaves and flowers
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4
Q

secondary inflorescence meristems

A
  • the axillary buds of the cauline leaves
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5
Q

inflorescence meristem vs flowers

A
  • inflorescence meristem has indeterminate growth

- flowers have determinate growth

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6
Q

what are the four different types of organs in floral meristems?

A
  • sepals
  • petals
  • stamen
  • carpels in concentric rings called whorls
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7
Q

initiation of carpels

A

The initiation of the carpels consumes all of the meristematic cells in the apical dome

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8
Q

what are the three types of genes that regulate floral identity?

A
  • meristem identity genes
  • floral organ identity genes
  • cadastral genes
  • These are groups of genes from which individual genes continue to be discovered via “loss of
    function mutants”
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9
Q

meristem identity genes

A

encode transcription factors that induce organ identity
- Must be active for the immature primordia at the shoot or inflorescence apical
meristem to become a floral meristem

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10
Q

floral organ identity genes

A

encode transcription factors that directly control floral
identity
- Homeotic genes that act as major developmental switches to activate the
genetic programing for a specific structure

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11
Q

cadastral genes

A

encode transcription factors that act as spatial regulators of the floral
organ identity genes by setting boundaries for their expression
- from French word cadastre, meaning ‘register of property’

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12
Q

ABC model

A

Floral organ identity genes determine floral organ patterning according to an elegant system, as
predicted by the ABC model proposed in 1991

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13
Q

how is each whorl determined by the three gene activities?

A
  • Type A activity alone specifies sepals
  • Type A activity with type B activity specifies petals
  • Type B activity with type C activity specifies stamens
  • Type C activity alone specifies carpels
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14
Q

type A

A

Type A activity controls organ identity in the first and second whorl

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15
Q

Type B

A

Type B activity controls organ identity in the second and third whorls

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16
Q

Type C

A

Type C activity controls organ identity in the third and fourth whorls

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17
Q

what is a loss in type A?

A

loss of type A activity results in the formation of carpels instead of sepals in the first whorl
and of stamens instead of petals in the second whorl

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18
Q

what is a loss in type B?

A

Loss of type B activity results in the formation of sepals instead of petals in the second whorl
and of carpels instead of stamens in the third whorl

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19
Q

what is a loss in type C?

A

Loss of type C activity results in the formation of petals instead of stamens in the third whorl,
and the formation of a new flower instead of carpels into the fourth whorl

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20
Q

what is a loss in type A, B, and C?

A 
- Loss of A, B, and C activity results in the formation of a pseudoflower in which all floral organs
are replaces with green leaf-like structures
- Since AB and C genes were identified another class of floral homeotic genes, class E
genes (D genes are required for ovule formation).
21
Q

when do annual plants produce flowers?

A
  • within a few weeks after germinating
22
Q

when do perennial plants grow flowers?

A
  • example: forest trees
  • may grow 20+ yeas before producing flowers
  • Thus size or age of a plant is an internal factor controlling the switch to reproductive
    development
23
Q

autonomous regulation

A

plants flower entirely according to internal cues

24
Q

obligate response

A

plants that exhibit an absolute requirement for environmental cues in order to flower

25
Q

facultative response

A

flowering is promoted by environmental cues but will eventually occur in the
absence of such cues

26
Q

what is the phase changes , development stages, and trajectory reproduction in higher plants?

A
  • juvenile phase
  • adult vegetative phase (ability to form reproductive structures)
  • adult reproductive phase
27
Q

how is the transition from juvenile to adult frequently displayed?

A
  • changes in vegetative characteristics such as leaf morphology, phyllotaxy, and thorniness
28
Q

how can the transition from juvenile to adult be seen in a single leaf?

A
  • The juvenile pinnately-compound leaf is replaces by adult phyllodes
    (flattened petiole) and transition leaves can be observed (juvenile at
    base adult at tip)
29
Q

combinatorial model

A
  • shoot development can be described as a series of
    independently regulated, overlapping programs, which modulate the expression of a common
    set of processes
  • Thus, different shoots on a given plant may be in different phase sand different areas of
    a given shoot can be in different phases, and different areas of a given leaf can be in
    different phases
30
Q

where does developmental phase changes occur first?

A
  • tends to occur first at the base of the shoot
31
Q

in rapidly flowering herbacious species, how long does the juvenile phase last?

A
  • may only last a few days
32
Q

in woody species, how long does the juvenile phase last?

A
  • more prolonged juvenile phase, can last for decades
33
Q

what happens once a meristem has switched to the adult phase?

A

only adult vegetative structures are

produced culminating in floral evocation

34
Q

what are the two stages in floral evocation?

A
  • competence
  • determination
  • A bud is competent if it is able to flower when given the appropriate signal, which leads
    to determination
35
Q

circadian rhythms

A
  • some flowers can open during the day and close at night
  • organisms can sense and respond to the time of day
  • attuned to light/dark cycles
36
Q

endogenous oscillator

A
  • internal pacemaker
  • exists such that the cycles can continue
    in the absence of external cues, in continuous light or darkness
37
Q

what are the three parameters for circadian rhythm?

A

period (time between comparable points in the cycle,
e.g., peaks); phase (recognizable features, e.g., peaks for troughs), and amplitudes (distance
between peaks and troughs)

38
Q

what happens to circadian rhythm in constant light or darkness?

A
  • becomes free-running and depart from an exact 24 hour period?
39
Q

photoperiodism

A

he ability of an organism to detect day length, to allow an event to occur at
a particular time of year, i.e., to show a seasonal response

40
Q

short day plants (SDPs)

A

flower only in short days, or flowering is accelerated by short days
- flowing SDPs occurs only when day length is less than a critical day length (or night length
exceeds a critical night length)
- wait till the end of summer or fall (sometimes winter) to flower

41
Q

long day plants (LDPs)

A

flower only in long days, of their flowering is accelerated by long days
- Flowering in LDPs is promoted when the day length exceeds a critical day length (or night length
is shorter than a critical night length)
- will wait till spring or early summer to flower

42
Q

day neutral plants

A

species that will flower under any photoperiodic condition

43
Q

where is the site of perception of the photoperiodic signal?

A

the leaf

- The treatment of a single leaf of a SDP with short photoperiod is enough to trigger flowering in that plant

44
Q

how do plants measure day length?

A
  • by measuring the length of the night?
  • Giving a short flash of light i.e., a “night break” during a long night cancels the effect of the long-night, and disrupts flowering in SDPs and triggers flowering in LDPs
45
Q

what is the primary photoreceptor in periodism?

A
  • phytochrome
  • If a night break is given as red light, it has the effect of disrupting SPD flowering and triggering LDP flowering, which can be reversed by far-red light
46
Q

Vernalization

A
  • the process whereby flowering is promoted by a cold treatment given to a fully hydrated seed or to a growing plant
  • Without the cold treatment, plants that require vernalization show delayed flowering or remain vegetative
  • some plants must reach a minimal size before they become sensitive to low temperature
  • effective temp range is from below freezing to about 10 degrees
  • occurs primarily in the shoot apical meristem
47
Q

when are winter annuals sensitive to vernalization?

A

respond to low temperature very early in their life cycle

48
Q

florigen

A
  • grafting studies revealed there was a transmissible floral stimulus
  • experiment: grafting experiments showing that noninduced
    receptor plants were stimulated to flower by being joined to a leaf or shoot from a photoperiodically induced donor plant
  • is self-propagating
  • macromolecules and specific mRNAs for given genes would travel to the phloem into the shoot apical meristem via plasmodesmata

Plant Physiology (21 decks)

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