Plant Responses - Module 5 Flashcards

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1
Q

What are 3 main uses of commercial plant hormones?

A
  1. Control of ripening
  2. Hormone rooting powder and micropropagation
  3. Hormonal weedkillers
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2
Q

How are plant hormones used to control the ripening of fruit?

A

Plants will be harvested prior to ripening so they are hard and less likely to be damaged during transport

Once ready to be sold they are exposed to ethene - the hormones that makes them ripe

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3
Q

How are plant hormones used commercially for micropropagation?

A

Adding auxins to cut shoots promotes the growth of new shoots, thus enhancing the success of propagation of new plants from cuttings

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4
Q

How are plant hormones used commercially in hormonal weedkillers?

A

As interactions between plant hormones are balanced to prevent growth, the interruption of this balance may disturb the metabolism of the plant and subsequently kill it

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5
Q

What hormones are used in weedkillers and what effect do they have on the plant?

A

Synthetic dicot auxins, impact the metabolism of a plant and they die

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6
Q

What is a tropism?

A

Plant growth response to a stimuli from one direction

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7
Q

What is a phototropism?

A

Plant growth response to light

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8
Q

How do phototropism’s occur?

A

Occur as a result of the movement of auxins across the shoot or root (if the root is exposed to light) that is stronger on one side than the other

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9
Q

What way will shoots grow in regard to light?

A

Shoots are positively phototropic and will grow towards light

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10
Q

What way will roots grow in regard to light?

A

Roots are negatively phototropic and will grow away from the light

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11
Q

What plant hormones controls stomata control?

A

ABA hormone causing stomata to close

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12
Q

Why do plant hormones control the stomata?

A

To open the stomata to cool the plant and close the stomata in order to conserve water

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13
Q

What is a specific response of the mimosa pudica?

A

Plants folding in response to touch
- potassium ion movement and osmotic water movement allow the leaves to curl and unfold scaring herbivores and dislodging insects

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14
Q

What do tannins do as a plant chemical defence?

A

Tannins are toxic to insects as well as contain a phenol compound which is bitter

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15
Q

What do alkaloids do as a plant defence chemical?

A

Contain bitter nitrogenous compounds and are toxic to animals acting as poison

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16
Q

What do terpenoids do as a chemical plant defence?

A

Toxic to insects and fungi

17
Q

List some physical defences a plant may have to protect itself [4]

A
  1. Thorns
  2. Barbs
  3. Spikes
  4. Stings
18
Q

What is a pheromone? And give an example in plants

A

A chemical made by an organism affecting the social behaviour or other organisms in the same species

E.g maple trees release pheromones when under attack telling leaves on other branches to deposit callouses as a defence

19
Q

What are VOC’s in plants?

A

VOC’s are volatile organic compounds which act in a similar way to pheromones but interact with insects rather than other plants

20
Q

Where are auxins made?

A

Auxins are made in the roots, shoots and meristems of a plant

21
Q

Why do plants grow in the dark more rapidly?

A

Because they are trying to reach light in order to photosynthesise

22
Q

What is geotropism?

A

Plant growth response in regard to gravity?

23
Q

How do shoots response to gravity?

A

Shoots are negatively geotropic and will grow upwards

24
Q

How do roots respond to gravity?

A

Roots are positively geotropic and will always grow downwards

25
Q

How do gibberellins affect elongation of plant stems?

A

Gibberellins affect the length of the internodes - regions between leaves on a stem

26
Q

How are gibberellins involved in seed germination?

A

Evidence suggests gibberellins switch on genes that produce amylases and proteases - digestive enzymes required in germination breaking down the food stores in the seed

27
Q

What are the two pieces of experimental evidence that proves gibberellins are involved in seed germination?

A
  1. Scientists breed mutant seeds which lack the gene to make gibberellins - the seeds do not germinate. If gibberellins are then applied externally they will germinate
  2. If gibberellin inhibitors are applied the seed will not germinate, if taken away the seed will germinate
28
Q

What are auxins?

A

Growth stimulant hormones produced in plants

29
Q

How do auxins affect the main apical shoot of a plant?

A

Auxins affect the plasticity of the cell wall, meaning it will stretch more easily

They do this by binding to receptors on cell membrane causing pH to drop to the optimum 5, for enzymes to keep cell wall flexible

30
Q

What effect do high concentrations of auxins have on a plant?

A

High concentrations of auxin suppress lateral growth of shoots resulting in apical dominance

31
Q

What is apical dominance?

A

Apical dominance is the occurrence of auxins preventing lateral shoot grown

32
Q

What experimental evidence is there to show that auxins have an impact on apical dominance?

A

If the apical shoot is removed, lateral shoots will grow faster and if auxins are reapplied to apical shoot the growth of lateral shoots will decrease again

33
Q

What do low concentrations of auxins promote?

A

Root growth

34
Q

What is a synergism?

A

When different plant hormones work together resulting in a greater response than the one provided when the hormone acts alone

35
Q

What is an antagonism?

A

When plant hormones have the opposite affect and the balance of the hormones determines the effect on the plant

36
Q

Which hormones are involved in the falling of leaves on trees?

A

Auxins and ethene

37
Q

How do auxins and ethene cause plants to drop their leaves? [5]

A
  1. As light levels fall, concentration of auxins fall
  2. Leaves response to fall in auxin by producing ethene
  3. Ethene stimulates production of digestive enzymes
  4. Digestive enzymes weaken cell wall at ABSCISSION ZONE
  5. Vascular bundles seal, Leaf falls
38
Q

How does a decrease in temperature affect plants?

A

If cells freeze membranes are disrupted and the plant will die

39
Q

How have plants adapted to prevent freezing?

A

Cytoplasm of plant cells contain solutes that lower the freezing point e.g sugars, amino acids and proteins