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botany > Growth and Development & Plant Hormones Part 1 > Flashcards

Growth and Development & Plant Hormones Part 1 Flashcards

1
Q

Growth results from:

A

– cell division
– cell enlargement

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2
Q

Development

A

coordination of growth and differentiation into
tissues, organs, and the whole organism

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3
Q

Plant hormone

A

Naturally occurring organic substance produced in minute
quantities in one part of the plant and then transported to
another part of the plant where it controls or affects growth and
development

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4
Q

Plant hormone

A

Present in nanogram/gram fresh weight
– (1 nanogram = 1.0×10-9 grams)

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5
Q

Plant growth regulators:

A

– Both natural and synthetic substances that affect plant
development as hormones do
– Includes plant hormones
– Also active at low concentrations

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6
Q

Major Groups of Known Plant Hormones

A
  • Auxins
  • Gibberellins
  • Cytokinins
  • Ethylene
  • Abscisic Acid
  • (Brassinosteroids)
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7
Q

Auxein (Greek) =

A

to increase

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8
Q

IAA (indole acetic acid)

A
  • promotes cell enlargement
  • sometimes promotes cell division
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9
Q

Charles Darwin and his son Francis provided

A

early evidence for
the existence of auxin

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10
Q

auxins have positive effects but at high concentration it can also

A

Auxins have growth promoting and other positive effects BUT at
high concentration auxins can inhibit growth

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11
Q

whats more sensitive to auxin roots or shoots

A

Roots more sensitive to auxin than shoots

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12
Q

adding auxin to roots can

A

inhibit growth

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13
Q

What is more sensitive to auxin

dicots or monocots

A

Dicots mores sensitive to auxin than monocots

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14
Q

Some herbicides contain

A

2,4D (synthetic auxin)
that kills dicot weeds

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15
Q

Auxin is synthesized in

A

meristematic regions

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16
Q

where specifically is auxin synthesized in meristematic regions

A

-shoot tips
-root tips
-germinating seeds

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17
Q

Auxin also synthesized in

A

– young, rapidly growing leaves
– developing flowers
– young embryos following fertilization.

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18
Q

Polar Transport of IAA

where

A

In the shoot, Polar Transport of IAA in
parenchyma cells in contact with vascular
bundles.

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19
Q

Polar Auxin Transport

As it is transported downwards, it causes:

A

– Root initiation of cuttings
– Vascular tissue differentiation
– Inhibition of axillary bud growth

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20
Q

Roles of Auxin: 1

A

1) Causes Root Initiation

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21
Q

1) Causes Root Initiation

A

-Occurs naturally when a
cutting is placed in
water

-Auxin can be added to
the base of cuttings to
enhance the process of
root initiation

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22
Q

Auxin is the active ingredient in rooting powders.

A

rooting powders

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23
Q

too much rooting powder can

A

inhibit
root growth.

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24
Q

role 2 of auxin

A

Auxin Causes Vascular
Tissue Differentiation

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25
Q

Auxin Causes Vascular
Tissue Differentiation

A

When the xylem of a plant stem is
cut, new xylem forms around the
wound.

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26
Q

evidence for a role of
auxin in xylem differentiation

A

-In this demonstration, the top of
the plant was cut off to remove the
tip of the plant, the natural source
of auxin.
* The plant was wounded and the
vascular tissue was cut
* IAA was added in a paste above the
wound, and the xylem regenerated
around the wound without the tip
of the plant

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27
Q

Roles of Auxin 3

A

Inhibits the growth of lateral buds, promoting
apical dominance (tip of plant (apex) is dominant
over lateral buds)

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28
Q

Auxin in an agar
block will also
substitute for

A

the tip

29
Q

There is more auxin near the

A

tip of the plant

30
Q

Growth of the axillary buds is
more inhibited closer to the

A

tip

31
Q

If the tip is removed, the
axillary buds will grow
because the

A

main source of auxin has been removed

32
Q

If the tip of a plant is cut off the

A

axillary bud will grow

33
Q

If the tip is cut off and replaced with auxin

A

(axillary) buds do not grow

34
Q

apical dominance
Strong in trees

A

with conical
shapes
(e.g. Pines, spruces, firs)
Norfolk Island Pine

35
Q

Apical Dominance

A

Weak in trees that branch more
often (e.g. Elms, ashes, willows)
Weeping Willow

36
Q

roles of Auxin 4

A

4) Involvement in tropisms

37
Q

tropism

A

directional response of a plant part to an
external stimulus in which the direction of the
response depends on the direction of the stimulus

38
Q

Positive phototropism of shoots

A

More auxins accumulate on the side in the shade, so the cells grow faster on the shaded side, making the shoot grow towards the sun.

39
Q

b. Negative gravitropism of shoots

A

Shoots grow away from the direction of gravity

40
Q

c. Positive gravitropism of roots

A

Shoots grow toward the direction of gravity

41
Q

Roles of Auxin Continued 5

A

5) Inhibits leaf and fruit abscission.

42
Q

Leaf Abscission in the Autumn

A

-Young leaves in spring and summer produce auxin
that travels through the petiole preventing
abscission
* Older leaves in autumn no longer produce enough
auxin and the abscission zone forms.

43
Q

Roles of Auxin Continued 6

A

6) Promotes flowering in pineapples

44
Q

G) Roles of Auxin Continued 7

A

7) Stimulates fruit development

45
Q

Parthenocarpy:

A

seedless fruits

46
Q

Some species will produce seedless fruits after
spraying the flowers with

A

auxin early in ovule
development:
– Tomatoes
– Eggplants
– Cucumbers

47
Q

Apple Orchards auxin

A
  • Spray with auxin:
    – to promote uniform flowering
    – to promote uniform fruiting
    – to prevent early abscission of fruits
48
Q

Roles of Auxin: 8)

A

controls weeds

49
Q

2,4-D and 2,4,5-T herbicides (synthetic
auxins) in

A

Agent Orange (Defoliant in
Vietnam War)

50
Q

2,4,5-T banned for most uses in 1979 due
to

A

dioxin contaminants
* Leukemia
* Miscarriages
* Birth Defects
* Lung & Liver Diseases

51
Q

2,4-D is

A

still used
* Moderate toxicity for mammals and birds

52
Q

Roles of Auxin Continued 9

A

9) Promotes cell division in tissue culture

53
Q

Gibberellins =

A

GA’sa

over 135 diffrent kinds

54
Q

Gibberellic acid effects

A

– Growth promoting and other positive effects
– Promotes cell division and cell enlargement

55
Q

Discovery of Gibberellins (GA’s)

A

1) In Japan in the 1930’s (unknown in Western part of World)

56
Q

2) Foolish seedling disease (Bakane)

A

– Gibberella fujikuroi
– Culture medium that fungus was in or fungal extract caused symptoms
-Infected seedlings exhibit abnormal elongation and in severe cases stunting leading to death. It led to the discovery of GA.

57
Q

Roles of GA’s 1

A

1) Promote stem elongation of intact plants

58
Q

Cabbage rosettes

A

bolt and flower
following treatment with gibberellins.
*Bolting typically occurs due to low
temperatures and longer days.
*GA’s substitute for environmental
cues.

59
Q

Affects of Added GA’s on Stems

A
  • Short bush beans become climbing pole beans
  • Genetically dwarf rice, maize, peas become
    phenotypically tall.
  • Genetically tall plants have little response to
    added GA’s
60
Q

C) Roles of GA’s continued 2

A

Promote germination of dormant seeds and
growth of buds.

61
Q

C) Roles of GA’s continued 3

A

3) Can cause flowering.

62
Q

C) Roles of GA’s continued 4

A

4) Promotes fruit development and formation

63
Q

GA and promoting fruit gas use (grapes and its costs)

A

-Used to increase the size of Thompson seedless
grapes and makes less tightly packed bunches.
– Costly as Gibberella fujikuroi is still the source of
GA3

64
Q

Roles of cytokinins

A
  1. Promote cell division (cytokinesis)
  2. Produced in roots
    * Promotes shoot formation
    * Promotes growth of lateral buds
  3. Cause cell division in tissue culture
    * also differentiation of shoots in tissue culture
65
Q

Buds closer to tip
of plant have more
auxin and less

A

cytokinins from the
roots, so buds are
inhibited.

66
Q

Buds at nodes
closer to base of
plant have more

A

cytokinins from the
roots and less auxin
from the tip, so
buds are less
inhibited and they
start to grow.
Buds closer to tip
of plant have more
auxin and less
cytokinins from the
roots, so buds are
inhibited.
Cytokinins from Roots also Affect
Growth of Axillary Buds

67
Q

High cytokinin to
auxin ratio

A

promotes shoot
differentiation
promotes root
differentiation

68
Q
A

botany (25 decks)

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