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Life Sciences > Responding to the environment: Plants > Flashcards

Responding to the environment: Plants Flashcards

1
Q

What are plant hormones?

A

Molecules that are produced naturally within plants.

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2
Q

Do plant hormones occur in high or low concentrations?

A

Low concentrations

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3
Q

What do plant hormones do?

A

Regulate the processes within the plant:

  • In cells and tissues, they influence:
    • growth
    • development
    • differentiation
  • Determine:
    • formation of:
      • flowers
      • stems
      • leaves
    • shedding of leaves
    • development and ripening of fruit
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4
Q

Do all plant cells respond to hormones?

A

No

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5
Q

Name the three different classes of plant hormones

A
  • Abscisic acid
  • gibberellins
  • auxins
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6
Q

Where do auxins occur in the plant?

A

In the:

  • Embryo of seed
  • Young leaves
  • Young fruit
  • Meristems of apical buds
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7
Q

What are some of the major functions of auxins?

A
  • Stimulate:
    • cell elongation
    • ethylene synthesis
    • fruit development
    • adventitious roots on cuttings
  • Tropic responses (phototropism and geotropism)
  • In vascular tissue, maintains:
    • apical dominance
    • differentiation
  • Inhibits flowering
  • Abscission before formation of abscission layer
  • Controls:
    • ageing
    • senescence
    • dormancy of seeds
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8
Q

Where does abscisic acid occur in plants?

A
  • leaves
  • stems
  • green fruit
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9
Q

What are some of the major functions of abscisic acid?

A
  • Stomatal closure
  • inhibits cell growth
  • dormancy
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10
Q

Where is gibberellin found?

A
  • meristems of apical buds
  • roots
  • young leaves
  • embryo
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11
Q

What are some of the major functions of gibberellin?

A
  • cell division
  • cell elongation
  • shoot elongation
  • seed germination
  • flowering in biennials
  • production of hydrolytic enzymes (in grains)
  • development of male flowers in monoecious plants
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12
Q

What do herbicides contain?

A

a synthetic plant growth hormone or auxin

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13
Q

Chemically, what are auxins or plant growth hormones classified as?

A

acids

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14
Q

In what form are herbicides applied?

A

Ester or salt form

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15
Q

What do herbicides induce?

A

Uncontrolled plant growth

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16
Q

What are broad-leaf plants called?

A

dicotyledons

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17
Q

Give one example of a dicotyledon

A

dandelions

A dicotyledon is a broad-leaf plant

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18
Q

What are narrow-leaf plants called?

A

monocotyledons

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19
Q

Give two examples of monocotyledons

A

grasses

cereal crops

Monocotyledons are narrow-leaf plants

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20
Q

Which are more susceptable to auxins, dicotyledons or monocotyledons?

A

dicotyledons

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21
Q

What are normally dicotyledons?

A

weeds

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22
Q

What are SELECTIVE HERBICIDES or SELECTIVE WEED KILLERS?

A

Herbicides that kill some plants, but not others

That are collectively called growth substances

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23
Q

What is the most important group of chemicals for plant growth?

A

Auxins

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24
Q

Where are auxins produced?

A

In the meristematic region of the growth tip of a:

  • shoot or root
  • plant embryo
  • young fruit
  • young leaves
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25
Q

Auxins move away from a…

A

Unidirectional light source

26
Q

Auxins are attracted by…

A

The force of gravity

27
Q

When auxins occur in the correct concentration, they…

A
  • stimulate cell division
  • stimulate cell elongation
28
Q

What is phototropism?

A

The growth response of a plant to a light source

29
Q

What is the growth response of a plant to light source due to?

A

An unequal distribution of auxins in the stem tip when exposed to a light source from one direction

30
Q

What is positive phototropism? Where does it occur?

A
  • Growth towards a light source
  • Plant stems
31
Q

What is negative phototropism? Where does it occur?

A
  • Growth away from a light source
  • In plant roots
32
Q

Auxins collect mainly on the ____ side of plants

A

Darker

33
Q

how do auxins behave in stems?

A
  • Stimulate cell expansion
  • Stimulate cell elongation

Darker side will grow faster. Results in stem bending towards the light source.

34
Q

What is geotropism?

A

Growth response of a plant towards gravity

35
Q

Why does a root grow straight down?

A

Auxins collect on the side-tip of the root and move upwards evenly

36
Q

What is the effect of auxins in roots?

A
  • Inhibits cell elongation

Therefore, the cells on the upper side of the root grow faster than the cells on the lower side of the root.

This makes the root grow TOWARDS gravity

37
Q

What is negative geotropism?

A

The upward growth of plant parts (growth against the force of gravity)

38
Q

What is positive geotropism?

A

The downward growth of plant parts. (this is growth towards the force of gravity)

39
Q

What are plant defence mechanisms?

A

Adaptations that have evolved in plants.

These adaptations improve their survival and reproduction rates by reducing the impact of herbivores.

40
Q

What are types of defence mechanisms used by plants?

A
  • chemical defences
  • mechanical defences
  • mimicry
41
Q

How can defensive chemicals be grouped into classes?

A

Based on their structures and how the plant makes them.

42
Q

Name some actions that function as the plants’ chemical defence mechanism

A
  • Interference with neurotransmitters
    • Addictive
      • Caffeine (coffee)
      • Morphine (poppy)
      • Nicotine (tobacco)
  • Odours
    • attract predators or parasites
      • kill damaging herbivore
    • Certain animal enzymes react with these compounds (poisonous)
  • Distateful and toxic secretions
43
Q

What are mechamical defences

A

external defences that discourage animals from feeding on them

44
Q

How can a plant’s stem or leaves be mechanially adapted?

A

They could have sharp prickles, spines or thorns.

These reduce feeding by a large group of ungulate herbivores.

Feeding is reduced by:

  • Restricting feeding rate
  • Wearing down molars
45
Q

Give one mechanical adaptation that can occur in some plant tissues?

A
  • Sharp toxic needles can occur in plant tissue
    • makes ingestion painful
    • damages mouth and gullet
    • enables plant’s toxins to enter bloodstream more easily
46
Q

What does “ungulate” refer to?

A

A large group of mammals that have hooves

47
Q

How can the structure of a plant be adapted to reduce herbivore impact?

A
  • Branching and leaf arrangement
    • Eg. Acacias have long spine in the part of the canopy but short spines in the part of the canopy where the giraffes cannot reach
48
Q

What are adventituous roots?

A

Roots that arise from an organ other than roots

49
Q

What are the two main components of vascular tissue?

A

Xylem and ploem

50
Q

What is apical dominance?

A

When the main central stem grows more strongly than others.

51
Q

What does “differentiation” refer to?

A

When distrinct cell types arise from other cells

52
Q

What can the stem also be called?

A

Petiole

53
Q

What is an abscission layer?

A

A layer that blocks off the supply of carbohydrates to the leaves

54
Q

What is leaf senescence?

A

Recycling of nutrients

55
Q

What is seed dormancy?

A

When seeds are prevented from germinating

56
Q

What is stomatal closure?

A

The closure of stoma (pores) on the underside of a leaf

This reduces water loss via transpiration

57
Q

What is a meristem?

A

Region of plant tissue found chiefly at the growing tips of plant roots and shoots

58
Q

What is a biennial plant?

A

A plant that lives for two years

59
Q

What does a hydrolytic enzyme do?

A

Catalyses the chemical bond making proteins, nucleic acids, starch, fats, phosphate esters, and other macromolecular substances.

60
Q

What is a monoecious plant?

A

Plants that contain both male and female flowers

61
Q
A

Life Sciences (7 decks)

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