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Biology 1 > Lecture 11- Plant growth > Flashcards

Lecture 11- Plant growth Flashcards

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1
Q

What are nutrients?

A

The major ingredients for macromolecules: hydrogen, oxygen, carbon, nitrogen

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2
Q

How does carbon enter the living world?

A

Photosynthesis using carbon dioxide from the air

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3
Q

How does hydrogen and oxygen enter plants?

A

Mainly as water

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4
Q

What mineral nutrients do plants need?

A

Phosphorus, magnesium, iron, sulfur

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5
Q

Where are mineral nutrients found?

A

In soil solution

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6
Q

What is phosphorus used for in plants?

A

Used in nucleic acids, ATP, phospholipids

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7
Q

What is sulfur used for in plants?

A

Proteins, coenzymes

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8
Q

What is magnesium used in within plants?

A

Chlorophll, ribosomes, enzymes

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9
Q

What is iron used in within plants?

A

Chromocytes, chlorophyll synthesis

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10
Q

In what form do plants take up mineral nutrients from the soil?

A

Iron form

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11
Q

What are autotrophs?

A

Organisms that make their own organic compounds from simple inorganic compounds

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12
Q

How do microenvironments direct a plants growth?

A

Encourages or discourages proliferation of a root system to direct plant growth

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13
Q

How do plants obtain more nutrients given that they are sessile?

A

Growth: extension of root system to mine new sources of mineral nutrients and water
Leaves and stem growth provides more oxygen and carbon

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14
Q

What happens to the roots of a plant as they grow?

A

They encounter a variable environment

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15
Q

What effect may animal droppings have on a plants roots?

A

Local high concentration of nitrogen

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16
Q

What may cause a tiny alkaline area?

A

Calcium carbonate particles in the soil

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17
Q

How does dead organic matter change the soil for a root?

A

Makes the area acidic

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18
Q

With the exception of nitrogen, where are mineral elements required by plants derived from?

A

Rocks

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19
Q

What is the criterion for calling something an essential element?

A

It is required for the plant to complete its life cycle (cannot be replaced)

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20
Q

What concentration of macronutrients is required?

A

1g per kg dry matter

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21
Q

What concentration of micronutrients is required?

A

less than 100milligrams per kg of dry matter

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22
Q

What is plant development?

A

The series of progressive changes that take place throughout its life

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23
Q

What are the 4 factors that regulate plant growth?

A
  • Environmental cues
  • Hormones (mediate environmental cues)
  • Receptors (sense environmental cues)
  • Genome (enzymes for development)
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24
Q

What plant is used as a model organism?

A

Arabidopsis thaliana- a weed in the Mustard family

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25
Q

Why is Arabidopsis thaliana a good model organism?

A
  • Small genome
  • Small body and seeds
  • Flowers and seeds quickly
  • Genes can be inserted or deleted
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26
Q

What are hormones?

A

Regulatory compounds that act at low concentrations, often at sites distant to where they were produced

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27
Q

What is the difference between hormones in plants and in animals?

A

In plants, many different cell types produce hormones

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28
Q

What other molecules are involved in plant development?

A

Photoreceptors (pigment molecules associated with proteins)

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29
Q

By what mechanism does light effect the development of a plant?

A

Light act on photoreceptors which regulate the processes of development

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30
Q

What determines the limit of a plants development?

A

The plant’s genome

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31
Q

What is a signal transduction pathway?

A

A sequence of biochemical reactions by which a cell generates a response to a stimulus

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32
Q

What amplifies a response to signals in plants?

A

Protein kinase (molecules which modifies mostly proteins by mostly phosphorylation)

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33
Q

What does it mean for a seed to be dormant?

A

Developmental activity is suspended (does not divide, expand or differentiate)

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34
Q

What does it mean for a seed to germinate?

A

To develop into a seedling

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35
Q

How does a germinating plant obtain nutrition?

A

Monomers are obtained by digesting polysaccharides, fat and proteins stored in the seed

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36
Q

How do some plants mobilize the reserves of nutrients in the seed?

A

Using hormones

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37
Q

When is germination complete?

A

When the radicle (embryonic root) emerges from the seed coat

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38
Q

What is the seed called after germination?

A

Seedling

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39
Q

How is development controlled after a seed germinates underground?

A

A series of photoreceptors

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40
Q

What is flowering?

A

The formation of reproductive organs

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41
Q

Describe early root development in monocots (such as corn)

A

Coleoptile projects from early shoot as it grows to the soil surface

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42
Q

What is the first step in seed germination?

A

Imbibition (uptake of water) due to differences in water potential- can exert tremendous force

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43
Q

What metabolic changes occur as a seed uptakes water?

A

enzymes are activated, RNA and proteins are synthesised, cellular respiration increases, metabolic pathways are activated

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44
Q

In many seeds, what is growth the result of?

A

Expansion of small, preformed cells (cell division does not occur during early stages of germination)

DNA synthesis occurs after the radicle ruptures the seed coat.

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45
Q

How does an embryo obtain nutrition?

A

Uses the reserves of energy/raw material stored in the seed coat

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46
Q

Where are nutrition and energy reserves found within an embryonic plant?

A

Cotyledon and endosperm (specialised nutritive tissue)

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47
Q

What is the typical activity of the hormone abscisic acid in plants?

A

Maintains seed dormancy and winter dormancy, closes stomata

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48
Q

What is the typical activity of auxins in plants?

A

Promote stem elongation, adventitious root initiation, fruit growth
Inhibit auxillary bud outgrowth

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49
Q

What is the typical activity of cytokinins in plants?

A

Inhibit leaf senescence, promote cell division and auxillary bud outgrowth, affect root growth

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50
Q

When is formation of reproductive organs initiated?

A

Flower formation begins when a plant reaches a certain size

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51
Q

How do some plants flower at certain times of the year?

A

They distinguish between seasons

52
Q

How do plants distinguish between seasons?

A

Photoreceptors absorb light to measure time

Hormones trigger flowering

53
Q

What are perennials? Give some examples.

A

Plants that continue to grow year after year, such as iris and elm

54
Q

What are annuals? Give some examples.

A

Plants which complete their life cycle in one year, then senesce and die. For example, petunia and marigold

55
Q

What does senesce mean?

A

Deterioration due to ageing

56
Q

What causes senescence?

A

Signals from the environment causes hormones such as ethylene to begin senescence

57
Q

Why does senescence occur?

A

Adaptation for producing more offspring

58
Q

Other than in annuals, where is senescence seen?

A

Perennials leaves at the end of the growing season- regulated by ethylene and auxin

59
Q

When might seeds remain dormant?

A
  • During unfavorable years
  • Not before a certain period of time
  • Not unless in specific environments
60
Q

What environments might cause a seed to germinate?

A

Digestive tracts, abrasive surfaces, soil microorganisms, fire, leaching

61
Q

Before a plant can photosynthesis, where does it obtain nutrition?

A

Food reserves in the cotyledon or endosperm

62
Q

What is the endosperm?

A

Tissue that surrounds the embryo

63
Q

How do angiosperms reproduce?

A

Sexually and asexually

64
Q

What is the advantage of sexual reproduction?

A

Genetic recombination gives diverse phenotypes

65
Q

What type of angiosperm reproduction is important in agriculture?

A

Both sexual and asexual

66
Q

What crops come from sexual reproduction?

A

-Annual crops grown from seeds:

Grains (wheat, rice, corn)
Soybeans

67
Q

What crops come from asexual reproduction?

A

Navel oranges, strawberries

68
Q

How did Navel oranges arise?

A
  • Single Brazilian Navel orange tree
  • Seedless
  • Propagated asexually
  • Aberrant flowers- part aborts and results in seedless fruit
69
Q

Why are strawberries propagated asexually?

A

They are highly heterozygous/ not true breeding

Propagated asexually to ensure desirable genotype

70
Q

What are the 4 groups of organs and what are they derived from?

A

Derived from modified leaves

  • Carpels
  • Stamens
  • Petals
  • Stepals
71
Q

What are the female and male sex organs?

A

Carpels- female

Stamen- male (staMEN- men are male)

72
Q

What is a pistil?

A

A structure composed of one or more carpels

73
Q

What is the base of the pistil called?

A

The ovary

74
Q

What does the ovary contain?

A

One or more ovules

75
Q

What do ovules contain?

A

A megasporangium- in which, the female gametophyte may develop.

76
Q

What is in the stamen?

A

A filaments with a two-lobed anther

77
Q

What does the anther consist of?

A

4 microsporangia fused together

78
Q

Where do male gametophytes begin their development?

A

Within the microsporangia.

79
Q

How are petals and sepals arranged?

A

Whorls (circles) or spirals around the carpels and stamens

80
Q

What do the petals constitute?

A

The corolla

81
Q

What do the sepals constitute?

A

The calyx

82
Q

What do all the flower parts attach to?

A

The stem tip called the receptacle

83
Q

What is alternation of generations in flowering plants?

A

Multicellular diploid generation alternates with multicellular haploid generation

84
Q

In angiosperms, which generation is the larger, more conspicuous one?

A

The diploid sporophyte generation

85
Q

Which generations produces flowers?

A

Diploid sporophyte generation

86
Q

What produces haploid spores?

A

The flowers of the diploid sporophyte generation

87
Q

What is produced in the megasporangia?

A

Megagametophytes (female gametophytes) called embryo sacs

88
Q

What is produced in the microsporgangia?

A

Microgametophytes (male gametophytes) called pollen grains

89
Q

What happens within the megasporangium inside the ovule to produce megaspores?

A

The megasporocyte divides meiotically to produce 4 haploid megaspores

90
Q

What happens after 4 megaspores have been produced/

?

A

All but 1 degenerate

91
Q

What happens to the surviving megaspore?

A

It undergoes three mitotic divisions to produce 8 haploid nuclei contained within a single cell- 3 nuclei at one end, 3 at the other and 2 in the middle

92
Q

What happens after the megaspore contains 8 nuclei in one cell?

A

Each develops a cell wall to make an eliptical, 8 celled megametophyte with 8 nuclei

93
Q

What is at the end of the megagametophyte?

A

Three cells- egg and 2 synergids

94
Q

What do synergids do?

A

Attract the pollen tube and receive the sperm nuclei

95
Q

What is at the opposite end of the megagametophyte?

A

3 antipodal cells which degenerate

96
Q

What is in the central cell of the megagametophyte?

A

Two polar nulcei which combine with one sperm nucleus

97
Q

What is the embryo sac?

A

The entire megagametophyte structure

98
Q

How does the microsporocyte developing into the microgametophyte within the anther?

A

The microsporocyte undergoes meiosis to produce 4 haploid microspores
Each microspore develops a cell wall and divides by mitosis to form two haploid cells in each pollen grain (microgametophyte)

99
Q

What are the two cells that make up the microgametophyte?

A

The generative cells and the tube cell

100
Q

What is pollination?

A

The transfer of pollen from anther to stigma

101
Q

How is self-pollination achieved in some plants?

A

Pollination occurs before the flower opens, such as in peas

102
Q

What is cross-pollination?

A

When pollen is transferred to a different individual

103
Q

What are common ways pollen is transported?

A

Wind, water, animals (insects, birds, bats)

104
Q

What are some characteristic features in plants that are wind pollinated?

A
  • Sticky or feather-like stigmas

- Many pollen grains

105
Q

What is self-incompatibility?

A

When plants reject pollen from their own flowers

106
Q

Why do some plants have self-incompatibility?

A

To promote out-crossing between different genotypes

107
Q

What gene is responsible for self-incompatibility?

A

The S gene

108
Q

How does the S gene determine compatibility?

A

If the S allele in pollen matches the S allele in the pistil, the pollen grain fails to grow

109
Q

What does the pollen tube do?

A

Deliver sperm cells to the embryo sac

110
Q

What is germination of a pollen grain?

A

The development of a pollen tube after a pollen grain lands on the stigma of a compatible pistil

111
Q

Why does pollen from other species not lead to germination?

A

Cell-cell signaling between pollen and stigma from the same species binds the pollen to the stigma
Foreign pollen drops off or fails to germinate

112
Q

In what ways does the pollen tube grow?

A

Grows through the style to reach the ovule

113
Q

How is downward growth of the pollen tube guided?

A

By chemical signals released by the synergids

114
Q

What happens after the pollen tube grows through the megasprogangium and reaches the embryo sac?

A

The generative cell undergoes one mitotic division to produce two haploid sperm cells

115
Q

What happens after two haploid sperm cells are produced?

A

Both sperm enter the synergid which degenerates and releases the sperm cells- one fertilises the egg to form a zygote, the other unites with the polar nuclei to form a triploid nucleus

116
Q

What happens after the sperm fuses with the egg cell?

A

The diploid zygote divides mitotically to produce the sporocyte embryo

117
Q

What does the triploid nucleus do next?

A

Divides by mitosis to form the nutritive endosperm

118
Q

What is the result of the first mitotic division of the zygote?

A

Asymmetric division of the cytoplasm

119
Q

What happens to the asymmetric zygote?

A

One daughter cell becomes the embryo, the other becomes a supporting structure called the suspensor

120
Q

What does the suspensor do?

A

Pushes the embryo against the endosperm to provide route for nutrients

121
Q

What does the embryo develop into in eudicots?

A

A heart stage as the cotyledons begin to form

122
Q

What happens to a eudicot embryo after the heart stage?

A

Further elongation leads to torpedo stage

123
Q

What is the structure of a eudicot embryo?

A

Shoot apex forms between cotyledons
Root apex forms from other end
Both contain meristematic cells

124
Q

What can happen in later stages of embryo development?

A

The seed loses water and becomes dormant

125
Q

What are integuments?

A

Tissues which surround the megasporangium and develop into the seed coat

126
Q

What does the carpel become?

A

The wall of the fruit that surrounds the seed.

Biology 1 (16 decks)

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