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Biology > 28. Plant Response > Flashcards

28. Plant Response Flashcards

1
Q

Stimulus def.

A

Any change in the environment which causes an organism to react/grow

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2
Q

Response def.

A

Is the reaction to the stimulus

eg. growth

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3
Q

Tropism def.

A

The change in growth of a plant in response to an outside stimulus.

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4
Q

Positive tropism

A

Growth is towards the stimulus

eg. shoot in response to gravity

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5
Q

Negative tropism

A

Growth is away from the stimulus

eg. root in response to gravity

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6
Q

Tropism types

A 
Geotropism-gravity
Phototropism-light
Thigmotropism-touch
Chemotropism-chemicals
Hydrotropism-water
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7
Q

Phototropism def.

Negative/positive in shoots/roots

A

Growth response to light
Negative: Roots grow away from light
Positive: Shoots grow towards light

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8
Q

Geotropism def.

Positive/negative

A

Def: Growth response to gravity
Neg: Shoots
Pos: Roots

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9
Q

Thigmotropism def.

example

A

Growth response to touch/contact

Vines wrap around objects which help support the plant

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10
Q

Chemotropism def.

example

A

Growth response to chemicals

eg. Pollen tubes grow down carpel in response to chemicals released by ovule
- Roots towards fertilisers in the soil

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11
Q

Hydrotropism def.

example

A

Growth response to water

eg. roots grow towards water

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12
Q

Advantage of tropisms

A

Allows plants to have the best conditions for growing.

eg. growth towards light so more light, more photosynthesis

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13
Q

What are internal factors affecting growth n a plant

A

Growth regulators

either growth inhibitors or promoters

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14
Q

Plant growth regulator def.
produced
transported by

A

Def: A chemical that controls the growth in a plant
Produced: Meristems regions-tips of roots and shoots
Transported by the phloem

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15
Q

Growth promoter def.

A

Increase rate of growth

eg. auxins such as IAA

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16
Q

Auxin
produced
How it works
Effects/Roles

A

Produced: Tip of plants, young seeds, young leaves
Works by: Loosening cell walls causing expansion of cells and elongation and therefore growth.
Effects: Causes tropisms, causes apical dominance, causes seeds to develop into fruits.

17
Q

How IAA controls phototropism

A

High IAA concentration on the shady side of shoot. Therefore cell elongation and quicker growth on shaded side. Which leads to bending due to uneven growth. Results in phototropism…plant growing in direction of light

18
Q

IAA role in geotropism

A

Low IAA concentration in roots causes roots to grow

19
Q

IAA role in apical dominance

A

Auxin produced at tip. Causes plant to grow up not sideways

20
Q

IAA role in fruit formation

A

IAA produced in developing seeds stimulates food store in seeds to form into fruits

21
Q

Examples of growth inhibitors

A

Abscisic acid

Ethene

22
Q

Abscisic Acid

How it protects against harsh conditions

A
  • Causes stomata to close saving water
  • Causes bud scales to form to protect buds during winter
  • Causes seed dormancy so stops germination in unfavourable conditions
23
Q

Ethene

why different from other growth regulators

A

Only one that is a gas

24
Q

Ethene where produced and role in plants

A

Produced: ripe fruits, decaying leaves

  • Causes ripening of fruit, fruit flavour and colour to develop.
  • Causes leaves to fall
  • Causes ageing of plants
  • Causes more ethene to be produced and further ripening of fruit.
25
Q

Uses of plant regulators in commercial plants

A
  1. Rooting powders-artificial auxin used for rapid root growth
  2. Tissue Culturing-plant tissue grown in high auxin concentration to form new plant
  3. Artificial Ethene-ripening of fruit
26
Q

Structural Adaptations in plants

A
  • Bark/ Epidermis/ Cuticle-prevent entry of microbes and reduces water loss
  • Thorns prevent plants from being eaten by herbivores
  • Stinging cell in epidermis prevent plants being eaten
27
Q

Chemical Adaptations in plants

A
  • If infected by microorganisms produces stress proteins which attack cell wall of microorg, stimulates neighbouring plant to respond to microorg, produces specialised cell wall to prevent entry.
  • Excessive heat: plants produce heat shock proteins to protect enzymes when temperatures are high

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