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Biology A2 Rafa > 5.5 Plant Responses > Flashcards

5.5 Plant Responses Flashcards

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1
Q

Define abiotic components

A

Components of an ecosystem that are non-living

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2
Q

Define biotic components

A

Components of an ecosystem that are living

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3
Q

Define tropism

A

A directional growth response in which the direction of the response is determined by the direction of the external stimulus

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4
Q

What are tannins?

A

Phenolic compounds, located in cell vacuoles or in surface wax on plants.
- prevent infiltration of pathogenic microorganisms

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5
Q

What are alkaloids?

A

Organic nitrogen-containing bases that have important physiological effects on animals, they may taste bitter for example

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6
Q

Examples of alkaloids

A
  • nicotine
  • quinine
  • strychnine
  • morphine
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7
Q

What are pheromones?

A

Chemical substances released by one living thing, which influences the behaviour or physiology of another living thing

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8
Q

Example of chemotropism

A

pollen tubes growing down the style, attracted by chemicals, towards the ovary where fertilisation takes place

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9
Q

Whats a non-directional response to an external stimulus called?

A

Nastic response

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10
Q

Example of nastic response?

A

Folding leaves in response to touch

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11
Q

Which plant is folds its leaves as a form of thigmonasty?

A

Mimosa pudica

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12
Q

What do cytokinins do?

A
  • promote cell division
  • delay leaf senescence (ageing)
  • overcome apical dominance
  • promote cell expansion
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13
Q

What does abscisic acid do?

A
  • inhibits seed germination and growth

- causes stomatal closure when the plant is stressed by low water availability

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14
Q

What do auxins do?

A
  • promote cell elongation
  • inhibit growth of side shoots
  • inhibit leaf abscission (leaf fall)
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15
Q

What do gibberellins do?

A
  • promote seed germination

- promote stem elongation

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16
Q

What does ethene do in plants?

A

-promotes fruit ripening

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17
Q

How can hormones move around the plant?

A
  • active transport
  • diffusion
  • mass flow in the phloem sap or in xylem vessels
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18
Q

What is apical dominance?

A

inhibition of lateral buds further down the shoot by chemicals produces by the apical bud at the tip of a plant shoot

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19
Q

What actually happens to a plant when the tip is cut off in terms of abscisic acid?

A

Apex gone, auxins cant regulate the concentrations of abscisic acid in lateral buds and so conc. drops
lateral buds grow

20
Q

What happens to a plant when the apex is cut off in terms of cytokinins?

A

Usually auxin is a sink for cytokinins and concentrates the in the apex
No auxin, cytokinins arn’t targeted to the shoot and is spread throughout the plant
Promotes bud growth elsewhere

21
Q

What happens when you apply a lot of cytokinins to normal plants?

A

Apical dominance is overwritten

22
Q

Whats an important auxin example?

A

IAA

23
Q

How does gibberellin cause seed germination?

A

water absorption by the embryo causes GA release

  • causes alpha amylase to be released
  • amylase breaks down starch so the embryo can use the energy for germination
24
Q

Where are there meristems?

A
  • apical meristem
  • roots
  • lateral bud meristem
  • intercalary meristems
  • lateral meristems (makes stem thicker)
25
Q

What piece of equipment is used to measure the effects of gravity on a plant?

A

Klinostat spins it round and round

26
Q

How does auxin work?

A
  • light causes auxin to go to shaded side
  • auxin causes active transport of H+ ions into cell wall
  • this decreases pH of cell wall
  • disrupts H bonding in wall and makes optimum pH for expansins to loosen walls
  • wall less rigid and can elongate as they take up water
27
Q

How do auxins affect roots and shoots?

A

Different levels of auxins affect them different

28
Q

How is auxin transported to the shaded side of plants?

A

By PIN proteins

29
Q

How is leaf loss in deciduous plants controlled?

A
  • Auxins inhibit leaf loss (auxins are produced by younger leaves, as the leaf gets older, less auxin is produced, leading to leaf loss)
  • Ethene stimulates leaf loss and is produced in ageing leaves (the abscission layer separates the leaf from the rest of the plant and ethene makes the cells in this expand and break the cell walls)
30
Q

How are hormones involved in stomatal closure?

A

Abscisic acid triggers stomatal closure

  • binds to receptors
  • Ca2+ ions enter through newly opened ion channels
  • Ca2+ go into the cytosol from the vacuole
  • Increased calcium conc. in cytosol causes other ion channels to open, allowing ions to leave the cell, RAISING its water potential
  • water leaves the guard cell by osmosis and it becomes flaccid and stomata close
31
Q

Commercial uses of auxins

A
  • herbicides (make weeds produce long stems instead of lots of leaves and they grow too fast, cant get enough water or nutrients and die)
  • rooting hormones (make plants grow roots) and cuttings
  • prevent leaf and fruit drop
  • promote flowering
  • seedless fruit
32
Q

Commercial uses of cytokinins

A
  • prevent yellowing of leaves

- plant mass production

33
Q

Commercial uses of gibberellins

A

-delay senescence of citrus fruits
-elongate apples
-less compact grape stalks so grapes can grow more
-brewing (produces amylase, breaks down starch into maltose)
sugar cane production (stimulate growth between nodes)
-plant breeding (induces seed formation)

34
Q

Commercial uses of ethene

A
  • stimulates enzymes that break cell walls, break down chlorophyll and starch into sugars - make fruit nice and soft eg banana
  • ripening in apples, tomatoes + citrus
  • fruit drop in cotton, cherry + walnut
35
Q

What inhibits the effects of ethene on plants?

A

silver salts

36
Q

What is a tropism?

A

Directional growth response

37
Q

What do synergic hormones do?

A

Amplify each others effects

38
Q

What do antagonistic plant hormones do?

A

Oppose each others effects

39
Q

How does growth occur in the meristem tissue?

A

By two processes:

  • cell elongation
  • cell division
40
Q

What is the Le gene responsible for?

A

producing enzyme that converts GA20 to GA1

41
Q

Is Le in tall or short?

A

tall

42
Q

Is le in tall or short?

A

short

43
Q

first experiments on role of auxins

in the control of apical dominance

A
  • suggestion = auxins from apical bud prevent later buds from growing
  • auxins applied to cut end and lateral buds do not grow
  • UNEXPECTED effect = upon exposure to oxygen, cells at cut end could have produced hormone that promoted lateral bud growth
  • new suggestion = normal auxin inhibits and low auxin promotes
44
Q

the experimental evidence for the role of

gibberellin in the control of stem elongation

A
  • when gibberellic acid on dwarf varieties = grow taller
  • compare GA levels in tall (Le) pea plants and dwarf (le) showed higher GA levels = taller
  • Le gene responsible for GA20 to GA1
  • plants with mutated gene are short
45
Q

the experimental evidence for the role of

gibberellin in the control of seed germination

A

when seed absorbs water, gibberellin released
goes to aleurone layer in endosperm region
enables production of amylase which = starch to glucose
=substrate for respiration = growth

46
Q

Describe mechanism of auxin

A

promotes active transport of H+ into cell wall
low pH = optimum for wall loosening enzymes (expansins) to work
break bonds between cellulose

Biology A2 Rafa (14 decks)

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