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Chapter 26: Response in the flowering plant

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Chapter 26: Response in the flowering plant Leaving Certificate Biology Higher Level Growth Regulation Growth of plants is controlled by growth regulators Growth ... – PowerPoint PPT presentation

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Title: Chapter 26: Response in the flowering plant


1
Chapter 26 Response in the flowering plant
  • Leaving Certificate Biology
  • Higher Level

2
Growth Regulation
  • Growth of plants is controlled by growth
    regulators
  • Growth regulator levels in the plant are
    controlled by tropisms
  • A tropism is the response of a plant to a change
    in its external environment or to a specific
    stimulus

3
Phototropism
  • Phototropism is the growth of a plant in response
    to light
  • Example is when plants bend towards a window

Geotropism
  • Geotropism is the growth of a plant in response
    to gravity
  • Example as soon as young root emerges from seed
    it grows towards gravity regardless of what
    orientation the seed was in

4
Hydrotropism
  • Hydrotropism is the growth of a plant in response
    to water
  • Example roots grow towards water

Chemotropism
  • Chemotropism is the growth of a plant in response
    to chemicals
  • Example roots grow towards minerals and away
    from heavy metals

Thigmotropism
  • Thigmotropism is the growth of a plant in
    response to touch
  • Example ivy growing up a wall or around a tree

5
Growth Regulators
  • A growth regulator is any chemical that controls
    the growth of a plant
  • Growth regulators are produced in extremely small
    amounts usually in the meristematic areas of a
    plant
  • Growth regulators are thought to be transported
    by vascular tissues to other areas of the plant
    but can also diffuse through ground tissue

6
Growth Regulators
  • The effects of growth regulators depend on
    various factors
  • The area where it is located
  • The concentration (high concentrations can have
    opposite effects to very low concentrations)
  • Growth regulators can cause growth or inhibit
    growth depending on interactions with other
    growth regulators

7
Examples of Growth Regulators
  • Growth promoters
  • Auxins (indole acetic acid IAA cause stem and
    root growth
  • Growth inhibitors
  • Ethene (ethylene) causes fruit to ripen
  • Abscisic acid helps plants deal with harmful
    conditions
  • causes stomata to close in very dry conditions
    despite presence of light)
  • Inhibits germination until ideal conditions are
    present

8
Phototropism
9
Anatomical Chemical Protection
  • Anatomical
  • Bark/dermal tissue/cuticle functions in
    protecting plant
  • Stomata and guard cells control water loss
  • Chemical
  • Heat shock proteins produced during times of
    stress to protect the enzymes within plant cells
  • Phytoalexins produced when plant is infected
    with microorganisms and help kill microorganisms,
    prevent further spread of the invader, and warn
    nearby plant cells

10
Mandatory Experiment to Investigate Effect of
IAA on Plant Tissue
  • Leaving Certificate Biology
  • Higher Level

11
Apparatus
  • Graduated cylinder
  • Weighing scales
  • Beakers
  • Stirrers
  • Spatula
  • Petri dishes
  • Pipettes
  • Deionised water
  • Cotton wool
  • Filter paper
  • Masking tape
  • Ruler
  • IAA( Indole Acetic Acid)
  • Ethanol
  • Cress seeds/Mustard seeds/Radish seeds

12
Method
  • Dissolve 100 mg IAA in 2 ml ethanol
  • Transfer to 1 L graduated cylinder and top up to
    1 L with deionised water to give 100 mg/L IAA
    stock solution
  • Transfer 10 ml IAA stock to first petri dish
    labelled A
  • Transfer 1 ml of this solution in A to B and top
    up with 9 ml deionised water
  • Mix B and transfer 1 ml of B to C
  • Repeat procedure until dish G
  • Dish H is control with 9 ml deionised water

13
Method (continued)
  • Place 5 cress seeds in line in the lid of each
    petri dish
  • Cover seeds carefully with filter paper
  • Transfer the serially-diluted solutions to each
    lid
  • Place layer of cotton wool into each lid and
    place base on
  • Seal each dish with masking tape and stand on
    sides in incubator set at 25 C

14
Results
  • After 2 3 days remove petri dishes and
    seedlings
  • Using ruler measure length of root and shoot for
    each concentration of IAA and record in table
  • Calculate increase or decrease for each
    concentration

15
Conclusion
  • IAA stimulates growth of roots and shoots up to a
    certain concentration
  • High concentrations inhibit growth
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