3.4.5 Control Systems in Plants Flashcards Preview

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Flashcards in 3.4.5 Control Systems in Plants Deck (34)
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1

Why do flowering plants respond to changes in their environment?

Increases their chances of survival

2

Give examples of how flowering plants respond to changes in environment

  • They sense direction of light and grow towards it to maximise light absorption for photosynthesis
  • Sense gravity so roots and shoots grow in right direction
  • Climbing plants have a sense of touch = find things to climb up and reach sunlight

3

What is tropism?

Response of plant to directional stimulus

4

How do plants respond to stimuli?

By regulating their growth

5

What is positive tropism?

Growth towards stimulus

6

What is negative tropism?

Growth away from stimulus

7

Name 4 types of tropisms

  • Phototropism
  • Gravitropism 
  • Hydrotropism
    • Responds to water
  • Chemotropism
    • Responds to chemicals

8

What is phototropism?

Growth of plant in response to light

9

Describe how the shoots and roots respond to light

  • Shoots are positively phototropic and grow towards light
  • Roots are negatively phototropic and grow away from light

10

What is gravitropism (aka geotropism)?

Growth of plant in response to gravity

11

Describe how the shoots and roots respond to gravity

  • Shoots are negatively gravitropic and grow upwards
  • Roots are positively gravitropic and grow downwards

12

What do plants use to respond to directional stimuli?

growth factors

13

What are growth factors?

Hormone-like chemicals that speed up or slow down plant growth

14

Where are growth factors produced?

In growing regions of plant (e.g. shoot tips, leaves)

& move to where they're needed in other parts of plant

15

What do auxins (growth factors) do?

  • Stimulate growth of shoots by cell elongation
    • Where cell walls become loose and stretchy so cells get longer

16

What does high concentrations of auxin result in?

Inhibits growth in roots

17

What is indoleacetic acid (IAA)?

Important auxin that's produced in tips of shoots in flowering plants

18

Describe how IAA is moved around a plant

Moves by diffusion and active transport over short distances & via phloem over long distances

19

What does an uneven distribution of IAA mean?

There's uneven growth of plant

20

Describe where IAA moves to control phototropism

IAA moves to more shaded parts of shoots and roots so there's uneven growth

21

Phototropism

State what happens to IAA and its effect in a shoot 

  • IAA concentration increases on the shaded side 
    • cells elongate and the shoot bends towards the light 

22

Phototropism

State what happens to IAA and its effect in a root 

  • IAA concentration increases on the shaded side
    • Growth is inhibited so root bends away from light

23

Describe where IAA moves to control gravitropism

IAA moves to the underside of shoots and roots, so there's uneven growth

24

Gravitropism

State what happens to IAA and its effect in a shoot 

  • IAA concentration increases on lower side 
    • cells elongate so shoot grows upwards

25

Gravitropism

State what happens to IAA and its effect in a root 

  • IAA concentration increases on the lower side 
    • growth is inhibited so the root grows downwards

26

Describe how bananas are artificially ripened before they are sold

  • Placed in ripening rooms where temperature and humidity are raised optimum levels
  • Ethene concentration is raised using a catalytic generator
  • Rooms are airtight to prevent gases escaping

27

Describe the role of ethene in fruit ripening

Ethene switch on genes for enzymes responsible for changing colour (hydrolyses), softening fruit (pectinases), increasing sugar content (amylases)

Synthesis of these enzymes require ATP and hence linked to increased respiration rate

28

Describe the role of abscisic acid (ABA) on a plant

  • Key role in plants response to environmental stress
  • Closing the stomata in response to low soil water or high salinity

29

When is abscisic acid (ABA) needed? Describe how ABA is transported

When soil water is low, ABA is transported from roots where it is synthesised up to shoots via xylem

30

Describe how stomata open

  1. H+ are actively transported out of guard cells causing inside to become more negative
  2. Negative charge causes inward K+ gates to open and allows K+ to enter guards cells
  3. K+ lowers water potential and water moves in by osmosis
  4. Guard cells become turgid

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