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Biology Leaving Cert > Plant Responses > Flashcards

Plant Responses Flashcards

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1
Q

stimulus

A

a change in the environment that causes response in an organism

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2
Q

plant growth regulators

A

chemicals (hormones) that control plant growth

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3
Q

auxins

A

hormones that regulate growth in plants

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4
Q

tropism

A

a response to a stimulus

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5
Q

phototropism

A

growth of a plant in response to light

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6
Q

geotropism

A

the growth response of a plant to gravity

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7
Q

thigmatropism

A

the growth response of a plant to touch

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8
Q

hydrotropism

A

the growth response of a plant’s roots to water

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9
Q

chemotropism

A

the growth response of a plant to chemicals

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10
Q

adverse external environment

A

surroundings which are harmful to organisms

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11
Q

stock solution

A

solution of known concentration

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12
Q

serial dilution

A

a series of dilutions of stock solution of known concentration

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13
Q

external factors that regulate growth

A

light intensity: required for energy for photosynthesis
day length: causing plants to flower
gravity: shoots grow up, roots grow down
temperature: affects enzyme activity

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14
Q

internal factors that regulate growth

A

plant growth regulators:
produced and secreted from: meristem
how transported: through vascular tissues in the stem
active in small amounts

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15
Q

how plant growth regulators and hormones in animals are alike

A

slow response and transmission speed
produced in one site and active in another
effect is widespread (in more than one part of the plant)

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16
Q

types and use of plant regulators: growth promotors

A

auxins
site of production: shoot tip + root tip
site of action: zone of elongation
example: indoleacetic acid (IAA)

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17
Q

auxins function

A

involved in phototropism (regulatory) and apical dominance (inhibitory)
higher concentration causes more growth, faster rate of cell division

18
Q

IAA

A

indoleacetic acid
site of production: meristem tissue at root tip and shoot tip
functions: causes stem and root lengthening
stimulates fruit formation

19
Q

describe apical dominance

A

apical bud produces auxin
auxin moves down through vascular tissue
allows the plant to grow vertically by inhibiting lateral bud growth and side branching

20
Q

mechanism of response : phototropism

A

stimulus: sunlight
1. IAA produced in meristem
2. diffuses to shady side of stem
3. cells on shady side elongate more than the sunny side (more IAA present)
4. stem bends toward the sun

21
Q

causes of unequal distribution of auxin

A

shoot: light shining in different directions

causes auxin to diffuse to shady side

22
Q

types and use of plant regulators: growth inhibitors

A

ethene

abscisic acid

23
Q

ethene

A 
inhibitor
site of production: ripe fruit
functions:
-promotes ripening of fruits
-promotes leaf fall and plant aging
24
Q

abscisic acid

A 
inhibitor 
site of production: stem, leaves
functions:
-inhibit germination: allows germination
-cause stomata to close in dry conditions and retain water
25
Q

commercially prepared growth regulators

A

gibberellins: production of seedless fruit
ethene: ripening of fruit, breaks down chlorophyll

26
Q

benefits of plant growth regulators to horticulturists

A

promote ripening
seedless fruit formation
micropropagation

27
Q

micropropagation

A

rapid multiplication of a plant using tissue culture methods which produce large numbers of identical plants

28
Q

advantage of phototropism

A

plant grows toward light providing more energy which increases photosynthesis rate

29
Q

advantage of geotropism

A

ensures roots always grow down to the soil

anchor the plant

30
Q

advantage of chemotropism

A

stimulates the pollen tube growth leading to fertilisation during sexual reproduction

31
Q

advantage of thigmatropism

A

provides support to plant for growth eg ivy on tree

32
Q

advantage of hydrotropism

A

allows plant roots to absorb more water

33
Q

positive tropism

A

growth response towards the stimulus
benefits as it provides best growing conditions
eg positive geotropism, roots grow with gravity

34
Q

negative tropism

A

growth response away from the stimulus

eg negative geotropism, shoots grow against gravity

35
Q

plant adaptations for protection

A

structural or anatomical adaptations
chemical adaptations
why: protection against ingestion by herbivores, disease from pathogens, water loss

36
Q

structural/anatomical adaptations

A
  1. spines, thornes
    -stop animals from eating them eg cacti, nettles
  2. guard cells
    -change shape when they lose water, stomata close
    controls transpiration rate
37
Q

chemical adaptations

A
  1. toxic chemicals/poisons
    - kill pests that eat them
  2. heat shock proteins
    - protect enzymes at high temperatures/pH outside optimum range
    - allow proteins to fold correctly
  3. stress proteins: response to invading pathogens
    - damage micro organisms/ form a strong cell wall to stop the pathogen
38
Q

results of experiment in control

A

the roots and shoots have grown as the seed itself has produced IAA
depending on the concentration of IAA solution, the roots and shoots in the control are longer than those that inhibited growth, and shorter than those that stimulated growth

39
Q

roots after experiment

A

lower conc. - stimulation, more growth

higher conc. - less growth

40
Q

shoots after experiment

A

lower conc. - less growth

higher conc. - stimulation

41
Q

experiment

A

plant used: cress seeds
why serial dilution: IAA works at very low concentrations so must be diluted, small amounts are difficult to make
safety: wear gloves when handling IAA as it is toxic

42
Q

control

A

no IAA just distilled water

Biology Leaving Cert (34 decks)

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