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biology 2022 paper 2 > Paper 2: Topic 5 Homeostasis & response - Plant hormones (LV) > Flashcards

Paper 2: Topic 5 Homeostasis & response - Plant hormones (LV) Flashcards

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1
Q

State an example of a plant growth hormone

A

Auxin

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2
Q

Describe the role of growth hormones in plants

A

To co-ordinate and control plant growth in response to light, water and gravity

AND

to control responses such as flowering and fruit production

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3
Q

State where in a plant auxin is produced

A

Shoot tips

Root tips

Hint: do not just say shoot and root

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4
Q

Describe 3 roles of auxin in plants

A

It controls the direction of growth of plants in response to light, water and gravity

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5
Q

Define the term phototropism

A

The directional growth of plants in response to light

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6
Q

Define the term geotropism

A

The directional growth of plants in response to gravity

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7
Q

Define the term gravitropism

A

The directional growth of plants in response to gravity

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8
Q

Define the term hydrotropism

A

The directional growth of plants in response to water

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9
Q

Describe the how different parts of a plant respond to light

A
  • Shoot tips grow towards the light
  • Root tips grow away from the light
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10
Q

Describe the how different parts of a plant respond to gravity

A
  • Root tips grow in the same direction of gravity (positive geotropism)
  • Shoot tips grow away from the direction of gravity (negative geotropism)
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11
Q

Explain how a shoot tip grows towards the light

A
  • Auxin is produced in the shoot tip
  • The auxin diffuses to the shaded side of the shoot tip
  • This casues unequal distrbution of auxin in the shoot tip
  • The high concentration of auxin causes the cells just below the shoot tip on the shaded side to elongate faster
  • This causes the shoot tip to curve towards the light
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12
Q

Explain how a shoot tip grows away from gravity

A
  • Auxin is produced in the unequally in the shoot tip
  • The auxin collects on the lower side of the shoot tip
  • This causes unequal distribution of auxin in the root tip
  • The high concentration of auxin causes the plant cells on the underside of the shoot tip on the lower side to elongate faster
  • This causes the shoot tip to curve upwards away from gravity
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13
Q

Explain how a root tip grows away from gravity

A
  • Auxin is produced in the unequally in the shoot tip
  • The auxin collects on the lower side of the shoot tip
  • This causes unequal distribution of auxin in the root tip
  • The high concentration of auxin inhibits growth in roots
  • This causes the plant cells on the top of the root tip to elongate faster
  • This causes the root tip to curve downwards towards gravity
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14
Q

Describe how plant cells in the root and shoot tip respond differently to auxin

A
  • Auxin stimulates plant cells to elongate in shoot tips
  • Auxin inhibits elongation in plants cells found in root tips
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15
Q

State 5 variables that must be controlled during an investigation studying the effect of light on plant growth

A
  1. Type of seeds
  2. Number of seeds
  3. Volume of water added to the seeds
  4. Temperature
  5. Light intensity and duration
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16
Q

State independent variable in an investigation studying the effect of light on plant growth

A

Direction of the light

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17
Q

State dependent variable in an investigation studying the effect of light on plant growth

A

The angle of the seedling

18
Q

Describe and explain what happens if a shoot tip is removed from a seedling

A

Description:

  • No directional growth occurs

Explanation:

  • If the shoot tip is removed no auxin is produced
  • Plant cells on both the lit and shaded side of the seedling elongate at the same rate
  • The seedling grows straight (with no curvature)
19
Q

State the term used to describe plant growth towards a stimulus

A

Positive tropism

20
Q

State the term used to describe plant growth away from a stimulus

A

Negative tropism

21
Q

State the term used to describe plant growth towards the light

A

Positive phototropism

22
Q

State the term used to describe plant growth away from the light

A

Negative phototropism

23
Q

State the term used to describe plant growth towards gravity

A

Positive geotropism / positive gravitropism

24
Q

State the term used to describe plant growth away from gravity

A

Negative geotropism / negative gravitropism

25
Q

State the term used to describe plant growth towards water

A

Positive hydrotropism

26
Q

State the term used to describe plant growth away from water

A

Negative hydrotropism

27
Q

Name the plant hormone important in initiating seed germination

A

Gibberellins

28
Q

Name the plant hormone important in controlling cell division and ripening of fruits

A

Ethene

29
Q

Give 3 uses of auxins in agriculture and horticulture

A
  1. Weed killers
  2. Rooting powders (to promote root formation)
  3. Promoting growth in tissue cultures
30
Q

State the use of ethane in the food industry

A

To control the ripening of fruit during storage and transportation

31
Q

Give 3 commercial uses of gibberellins in agriculture

A
  1. To end seed dormancy (i.e. promote germination)
  2. To promote flowering
  3. To increase fruit size
32
Q

Describe how auxins can be used as selective weed killers

A
  • Specialised auxins have been developed that only affect broad-leaved plants
  • If these auxins are applied to fields with crops in only the broad-leaved plants are affected
  • The broad-leaved plants dies as a result of disrupted growth
  • Narrow-leaved crop are unharmed
33
Q

Explain the benefits of using auxins as a selective weed killer

A
  • Selective weed killers only disrupt the growth of broad-leaved plants
  • This kills the broad-leaved plants
  • This means there is now more light and mineral ions available for the narrow-leaved plants
  • So the narrow-leaved plants now grow faster
34
Q

Describe how auxins can be used to stimulate root growth

A
  • The tip of a cutting can be dipped in rooting hormone powder
  • The auxins in the rooting hormone powder quickly stimulates root growth
35
Q

Describe how auxins are used in tissue culture

A
  • Auxins are added to the growth medium used in tissue culture
  • The auxins simulate the plants cells to divide to produce roots and shoots
36
Q

Give 2 techniques that involve the use of auxins to produce cloned plants

A
  • Tissue culture
  • Cuttings
37
Q

Explain the advantages of using gibberellins to control seed germination

A
  • Seeds can be forced to germinate at different times of the year
  • This means plants can be grown ‘out of season’
  • Using gibberellins ensures all the seeds in one batch will germinate at the same time (time efficient and cost effective for the gardener)
38
Q

Explain the advantages of using gibberellins to control flowering

A
  • Some types of plants require short days to stimulate flowering, other types of plants require long days
  • By using gibberellins plants can be forced to flower without any changes in their environment
  • The use of gibberellins can also result in larger flowers
39
Q

Describe how gibberellins can be used in fruit production

A

The application of gibberellins causes seedless fruit to be larger than it would be naturally (so that the seedless fruit is a similar size to the seeded fruit)

40
Q

Describe 2 effects ethene can have on plants

A
  • Ethene stimulates cell division causing increased plant growth
  • Ethene stimulates enzymes that cause fruit to ripen
41
Q

How can ethene be used commercially in controlling fruit ripening

A
  • Fruit can be picked in an unripe (harder) state
  • Ripening can be delayed by exposing the unripe fruit to chemicals that block ethene’s effect
  • This means the fruit can be stored or transported easily (less bruising and damage)
  • On arrival at the destination e.g. supermarket the fruit can be exposed to ethene to promote ripening
  • This make the fruit more desirable by the customer
42
Q

Explain what is happening in eaach area of the plant

A

biology 2022 paper 2 (6 decks)

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