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102 Growth & Development > Lecture 6 > Flashcards

Lecture 6 Flashcards

Plants weigh up internal and external signals to decide whether to flower or not. One signal is daylength which plants can measure and this controls photoperiodic flowering. Plants use genes , light signals, circadian clock to control their flowering.

1
Q

true or false; many plants flower at a precise time of the year

A

true

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2
Q

when do cherry blossoms and daffodils bloom

A

spring

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3
Q

when do pohutukawas bloom

A

early summer

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4
Q

Why is correct flowering time important for a plant

A

to ensure that seed production is completed successfully

  • important for people (harvest; high yield)
  • ensure successful reproduction
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5
Q

define photoperiodism

A

ability to sense and respond to daylength

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6
Q

true or false; photoperiod can control flowering

A

true

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7
Q

Who coined the term photoperiodism and when

A

Garner and Allard

1920

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8
Q

What are the 3 main classes of plants

A

short day plants
long day plants
day neutral plants

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9
Q

What does it mean by short day plant

A

(8h light/16hr dark)

flowering in response to short days and long nights

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10
Q

give 3 examples of short day plants

A

poinsettias
rice
soybean

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11
Q

What does it mean by long day plant

A

(16hr light/8 hr dark)

flowering in response to long days and short nights

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12
Q

give 3 examples of long day plants

A

Arabidopsis spinach
wheat
lettuce

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13
Q

What does it mean by day-neutral plant

A

flowering is not controlled by photoperiodism

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14
Q

give 4 examples of day-neutral plants

A

tomato
cucumber
sunflower
maize

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15
Q

what type of plant is morning glory

A

short day

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16
Q

what type of plant is arabidopsis

A

long day

17
Q

What does the GI (GIGANTEA) gene promote in Arabidospsis plants

A

promotes flowering

- mutation in the gene can inhibit flowering

18
Q

What does it mean by Circadian rhythm

A

occur every 24 hrs

  • 24 hr cycle
  • continues even in absence of exogenous cues
19
Q

What did De Marian propose about the movement of plants and when

A

1727

rhythms in leaf movement in the absence of daily cues

20
Q

What did Darwin propose about plant movement and when

A

1898

published the power of movement in plants

21
Q

Give 5 examples of activities that are controlled by the circadian clock

A
  • occur once every 24 hrs
  • leaf closure
  • flower opening and closing
  • stomatal opening and closing
  • Most biochemical and physiological processes
    eg. Carbon fixation, nitrate reductase, growth
  • gene expression rhythms ~ 30% Arabidopsis genes
22
Q

What is the function of the circadian clock

A

allows plants to get ready ahead of time

eg. photosynthesis (onset earlier) occurs in day time only
- most growth expansion of leaves occur at night (use their energy acquired during the day at night)
- seasonal behavior (eg. photoperiodic flowering)

23
Q

What are the three experiments to test out control in flowering

A
  1. ) Night break experiment (short day plants)
  2. ) different red light quality flashed on the plant (long day plants)
  3. ) grafting
24
Q

Describe the night break experiment

A
  • flash or light during the night
  • even a small interruption of light can ruin the perception for flowering
  • have indicated that night length is important

(length of dark period a critical parameter particularly for short day plants)

25
Q

Describe the experiment where far red light and red light were flashed at long day plants

A
  • flash of red light interferes with the flowering of chrysanthemums
  • far red light cancel the effect of red light
  • applies for both short and long day plants
  • phytochrome is the receptor perceiving the night break
26
Q

Describe the experiment of grafting

A

floral induction by day length is graft-transmissible

  • mobile plant flowering hormone florigen is graft transmissible (by splicing two plants together)
  • FT gene
27
Q

what are the commercial applications of controlling flowering of a plant

A

inducible flowering to specific dates of the year, such as Christmas, Valentines day

28
Q

Describe how poinsettias have been manipulated for commercial use

A

short day plants
need 14 hr dark
usually flower Feb/Mar(US)
Aug/Sep( NZ)

29
Q

When are poinsettias induced to flower in USA

A

at Xmas

by 14 hr dark treatments (Nov)

30
Q

when are poinsettias induced to flower in NZ

A

delayed from flowering until xmas by light flashes during the night

31
Q

What are other benefits of delaying flowering time

A

increase vegetative yield

- biofuel, forage, wood

32
Q

What are crops customized to

A
  • to different geographical regions and climates

eg. heat resistance

33
Q

What is florigen and where is it produced

A

produced in the leaves in inductive day lengths and transported to the shoot apex to convert meristems from vegetative to floral

102 Growth & Development (10 decks)

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