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Fundamentals of Plant Biology > Plant hormones > Flashcards

Plant hormones Flashcards

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1
Q

What are plant hormones?

A

Chemical messengers that are synthesized in one part of the plant, transported to another part, then do something in the cells of the receiving plant part

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2
Q

What do hormones do at a cellular level?

A

They bind to receptors and activate signalling pathways

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3
Q

What is the usually the end result of a signalling pathway activated by hormones?

A

Activate or deactivate gene transcription, cause secretion of compounds, activate protein kinases

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4
Q

What are 5 ways a plant can get more of a hormone?

A
  1. Increased transportation to the receptive plant area
  2. Activate the biosynthesis pathway
  3. Activate an inactive form
  4. Release from internal stores
  5. Uptake from other plants
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5
Q

What are 4 ways a plant can reduce the amount of a hormone?

A
  1. Break it down
  2. Inactivate it
  3. Sequester it away from the receptors
  4. Excrete into the environment or to other tissues
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6
Q

What are the 9 major classes of plant hormones?

A
  1. Auxins
  2. Gibberellins
  3. Cytokinins
  4. Ethylene
  5. Abscisic acid
  6. Brassinosteroids
  7. Jasmonates
  8. Salicylic acid
  9. Strigolatones
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7
Q

Are auxins essential for plant survival?

A

Yes, deficient mutations are lethal

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8
Q

What is the principal auxin in plants?

A

IAA

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9
Q

What do auxins do?

A

Maintain apical dominance by suppressing lateral growth

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10
Q

What did Darwin’s phototropism experiment look at?

A

Directional response to light stimuli, to determine if the tip was coordinating the plant’s phototropism or if each cell was coordinating their own movements

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11
Q

What were the 4 conditions that Darwin tested in his phototropism experiment?

A
  1. Cut the tip off
  2. Opaque cap on the tip
  3. Transparent cap on the tip
  4. Covered the stem
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12
Q

What happened to the plant’s phototropism when the tip was cut off in Darwin’s phototropism experiment?

A

Didn’t grow towards the light

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13
Q

What happened to the plant’s phototropism when the tip was covered with an opaque cap in Darwin’s phototropism experiment?

A

Didn’t grow towards the light

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14
Q

What happened to the plant’s phototropism when the tip was covered with a transparent cap in Darwin’s phototropism experiment?

A

Grew towards the light

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15
Q

What happened to the plant’s phototropism when the stem was covered in Darwin’s phototropism experiment?

A

Grew towards the light

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16
Q

What did Went’s phototropism experiment address?

A

Was there a diffusible substance produced by the tip of the shoot that mediated plant’s growth and bending towards the light

17
Q

What happened when Went replaced the tip of a seedling with a cut tip with an agar block saturated in the diffusible signal from the cut tip?

A

Growth resumed to the same level as the control

18
Q

What happened when Went put the saturated agar block on one side of the stem?

A

The side in contact with the block grew faster

19
Q

What effect does auxin have on a cell?

A

Activates a proton pump, which pumps protons into the cell wall and acidifies it

20
Q

Why does the acidification of the cell wall caused by auxin allow it to expand?

A

The acidity activates expansin, which breaks the connections holding the fibrils together

21
Q

How do plants move towards the light when signalled by auxin?

A

Auxin signalling causes cell walls to loosen on the side of the stem away from the light, so the stem bends towards the light

22
Q

Where is auxin produced?

A

SAM, young leaves, developing fruits and seeds

23
Q

How is auxin transported around the plant?

A

Through plasmodesmata and xylem

24
Q

What are 4 functions of auxins?

A
  1. Cell differentiation for wound healing
  2. Apical dominance
  3. Fruit development
  4. Tropisms and other plant movements
25
Q

When were gibberellins first discovered?

A

Foolish seedling disease in rice. Fungal pathogen was producing gibberellins and caused the plants to grow out of control and collapse

26
Q

What are 3 functions of gibberellins?

A
  1. Cell elongation
  2. Cell division
  3. Seed dormancy and germination
27
Q

Why do cells divide when you add coconut milk to them?

A

Contains cytokinins

28
Q

What are 4 functions of cytokinins?

A
  1. Cell division
  2. Cell differentiation
  3. Senescence
  4. Apical dominance
29
Q

What other hormone do cytokinins need to be in balance with to cause proper cell differentiation?

A

Auxins

30
Q

Why were trees with nearby gas lamps entering senescence too early?

A

Gas lamps were producing ethylene

31
Q

What are 2 functions of ethylene?

A
  1. Leaf abscission

2. Fruit ripening

32
Q

Where is abscisic acid synthesized?

A

Vascular tissues

33
Q

What are 4 functions of abscisic acid?

A
  1. Stress tolerance (water, heat, and salt stresses)
  2. Germination inhibition
  3. Symbiotic interactions
  4. Plant defence

Fundamentals of Plant Biology (25 decks)

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