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Biology > Polliniation And Fertilization > Flashcards

Polliniation And Fertilization Flashcards

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1
Q

Pollen consists of

A

Particles called pollen grains

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2
Q

Each pollen grain contains

A

Generative and tube nucleus

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3
Q

Autogamy

A

The pollen grains of the “same flower” fall on its stigma by itself

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4
Q

Geitonogamy

A

The pollen of another flower of the same plant falls on the stigma

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5
Q

Allogamy

A

The pollen of a flower of another plant of the same species falls on the stigma

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6
Q

Allogamy aka

A

Cross pollination

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7
Q

Cross pollination aka

A

Allogamy

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8
Q

Define pollination

A

Pollination is the process of transfer of pollen grains from the anther to the stigma

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9
Q

How has nature defined flowers to be

A

So that only the pollen of the same species of plant will survive and grow further to continue the process for reproduction.
The pollen of rest of the types will fail to germinate and will perish.

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10
Q

Name the 3 ways pollination occurs

A

Autogamy (same flower)
Geitonogamy (same plant different flower)
Allogamy (same species different plant)

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11
Q

What are the kinds of pollination?

A

Self pollination
Cross pollination

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12
Q

Define self pollination

A

The transfer of pollen from the anther to the stigma of the same flower (autogamy) or to the stigma of another flower of the same plant (geitonogamy)

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13
Q

On account of what is pollination between flowers of the same plant considered self pollination

A

On account of common genetic characters between all the different flowers borne on the plant.

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14
Q

What is cleistogamy

A

A type of pollination that occurs when flowers do not open even at maturity. Their reproductive structures (anthers and stigma) are hidden and lie close to each other. No external agent is required. They produce seeds through autogamy.

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15
Q

Cleistogamous flowers examples

A

Pea pansy

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16
Q

When are the conditions for self pollination occur

A
  1. Flower should be bisexual
    Or flower can be unisexual but must be monoecious
  2. Homogamy
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17
Q

What is homogamy

A

The anther and stigma of a flower mature at the same time

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18
Q

Reproductive structures

A

Stigma
Anther

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19
Q

Advantages of self pollination

A

It is surer in bisexual flowers where stamens and Carpels mature at the same time.
Parental characteristics are indefinitely preserved.
No wastage of pollen grains bc even small quantity of pollen suffices.
The flowers needn’t be large and showy nor produce scent and nectar.
This means great economy for plant, lots of nutrient material is saved.

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20
Q

Disadvantages of self pollination

A

Continued self pollination for many generations can lead to weakening of variety/species. The seeds produced through it are poor in quality and give rise to less vigorous offspring.
Weak/defective characters of breed can’t be eliminated
No new varieties yielded due to no intermixing this no chance for improvement in next gen.

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21
Q

Define cross pollination

A

Transfer of pollen from anthers of flowers of one plant to the stigma of a flower of another plant of the same species.

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22
Q

Chasmogamy

A

Plants have large flowers w open petals and exposed reproductive structures and require external pollinating agents. Hence they undergo cross pollination mainly

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23
Q

Examples of flowers that are chasmogamous

A

Oxalis
Hibiscus

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24
Q

Chasmogamous flowers examples

A

Oxalis
Hibiscus

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25
Q

Cross pollination advantages

A

Healthier offsprings
Abundant, viable seeds
New varieties may be produced by cross pollinating 2 different varieties of same species

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26
Q

Cross pollination disadvantages

A

Pollination isn’t always certain as a pollinating agent is always needed that might not be available at the proper time
Pollen has to be produced in large quantity for max chance of pollination meaning lots of wastage of pollen
Uneconomical process for plant as flowers need to be large produce nectar to attract pollination agents and nutrient material is wasted.

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27
Q

Which type of pollination is favoured by nature

A

Cross

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28
Q

What conditions favour cross pollination

A

Unisexuality
Dichogamy
Self sterility
Herkogamy
Heterostyly

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29
Q

Explain dichogamy

A

When there are different timings of maturation of Androceium and gynoecium.

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30
Q

Types of dichogamy

A

Protandry
Protogyny

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31
Q

Protoandry + Eg

A

Anther of flower matures earlier than stigma
Lady finger, sweet pea, Salvia, sunflower

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32
Q

Protogyny + Eg

A

The stigma of flower matures eaker than anthers
Custard apple
Peepal

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33
Q

Self sterility

A

Even if stigma received pollen from anthers of same flowers pollen won’t grow further. Thus only pollen from another plant of same species can complete the process of setting seeds

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34
Q

Self sterility ex

A

Ray florets of sunflower
Orchids

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35
Q

Herkogamy + Eg

A

In some flowers the pollen of a flower cannot reach the stigma of the same flower
Hood covering stigma is mechanical barrier in pansy flower

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36
Q

Heterostyly + eg

A

In these the stigma and anthers grow at different heights which does not favour self pollination.
Primrose, oxalis

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37
Q

4 differences between cross and self pollination

A

Self-pollination vs. Cross-pollination
Self-pollination
* Definition: The transfer of pollen grains from the anthers to the stigma of the same flower (autogamy).
* External agent: No external agency or agent is required.
* Maturation of parts: Male and female parts mature at the same time.
* Flower state: Can occur even when the flower is closed.
* Parental characters: Preserves parental characters.
* Variations: New variations are impossible, hence young ones cannot adapt to changed environmental conditions.
* New varieties: New varieties are not possible.
Cross-pollination
* Definition: The transfer of pollen grains from the anthers of one flower to the stigma of another flower of a different plant of the same species (allogamy).
* External agent: An external agent (wind, water, insect) is always required.
* Maturation of parts: Anthers and stigma mature at different times.
* Flower state: Can occur when the flower is open.
* Parental characters: Does not preserve parental characters.
* Offspring: Offsprings are healthier to adapt to environmental changes.
* New varieties: New varieties can be produced.

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38
Q

Entomophilous

A

Insect pollinated

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39
Q

Characteristics of insect pollinated flower

A

Large
Brightly coloured
Emir scent
Produce nectar (food for insect)
Sticky/spiny pollen grain (easily carried away by insect)
Sticky stigma doesn’t hang out from flower gen
Flowers in clusters esp when small

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40
Q

Eg of flower in cluster

A

Dahlia

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41
Q

Anemophilous

A

Wind pollinated

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42
Q

Wind pollination characteristics of flowers

A

Small
Not brightly coloured full green gen
No scent no nectar produced
Long stamens hanging out to be exposed to wind
Anther large and loosely attached to filament so slightest wind may be move them
Pollen is produced in v large amts
Light dry smooth pollen grains (easily carried away by wind)
Stigmas are feather and hang out of flower to trap pollen grains

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43
Q

Eg of wind pollinated flower

A

Maize

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44
Q

Versatile anther

A

Anther are large loosely attached to filament so slightest wind will move them

45
Q

Hydrophilous

A

Water pollinated (only in aquatic plants)

46
Q

Characteristics of flowers that are water pollinated

A
  1. Large amts of pollen
  2. In some plants pollen grains have specific gravity (density) almost equal to that of water so it remains floating below water surface
  3. Special cases: male flowers are such that they float on water surface until they meet female flowers
47
Q

When is male flower such that it floats on water surface go meet female flowers

A

Vallisneria

48
Q

Bird pollination + eg

A

Ornithophily
Bignonia, canna

49
Q

Elephant pollination

A

Elephophily

50
Q

Anther are large loosely attached to filament so slightest wind will move them

A

Versatile anther

51
Q

Elephophily example in detail

A

Rafflesia
Large flowers at ground level. The pollen grains of 1 flower get stuck to elephants feet and can be carried to stigma of another flower when the flower gets trampled by their feet.

52
Q

Define artificial pollination

A

When man himself transfers the pollen grains to the stigma of a flower

53
Q

In which civilisation was artificial pollination popular?
Which plant did they do it to?

A

Ancient babylonia
Palm flowers

54
Q

Artificial pollination aka

A

Artificial croasing

55
Q

Emadculation

A

Removal of anthers in young flowers for artificial pollination.

56
Q

Bagging

A

During artificial pollination they remove the anther in young flowers and then cover these flowers with plastic bags (bagging).

57
Q

How is artificial pollination done

A

Plant breeders and scientists remove the anthers in young flowers (emasculation) and cover these flowers with plastic bags (bagging).
Layer they pollinated these flowers with the pollen from the plants of the desired variety.

58
Q

Why is artificial pollination done

A

Done by scientists and plant breeders to evolve new varieties.

59
Q

Define fertilization

A

The union/fusion of the nuclei of the male and female gametes

60
Q

Each pollen grain has how many male gametes

A

2

61
Q

What produces female gamete

A

Ovule inside ovary

62
Q

What is the outerwall of pollen

A

Exine

63
Q

Inner wall of pollen

A

Intine

64
Q

Nucleus of pollen grain has divided into

A

Tube nucleus and generative (male) nucleus.

65
Q

The nucleus of pollen grain has _______ been divided

A

Already

66
Q

Further changes in pollen grain occur only if

A

If it has fallen on the stigma of a plant of same species.

67
Q

Describe the pollen grain (mature)

A

It is a cell with a double wall
Outer exine inner intine
Nucleus has already divided into tube and generative (male) nucleus
At this stage the pollen is transferred to stigma
Further changes in pollen grain occur only if it has fallen onto the stigma of plant of same species

68
Q

Inner part of ovary

A

Ovule

69
Q

Ovary matures to become

A

Fruit

70
Q

Ovule becomes

A

Seed

71
Q

How many ovules may be there

A

Single ovule - producing single seeded fruit
Many ovules - producing many seeded fruit

72
Q

Each ovule has one or two protective coverings

A

Integuments

73
Q

Each ovule has one or two protective coverings

A

Integuments

74
Q

Integuments have small opening called?
What does it facilitate?

A

Micropyle at one end
Entry of pollen tube

75
Q

What is enclosed by integuments

A

Nucellus

76
Q

What is nucellus

A

A mass of food laden cells

77
Q

Integuments

A

Each ovule has one or two protective coverings called integuments

78
Q

Embryo sac is located

A

Further inside nucellus

79
Q

Embryo sac contains

A

7 egg cells (3+3+1)
3 cells at micropylar end - 1 egg cell and 2 synergids
3 cells at opposite end called antipodal cells
1 large central cell containing two nuclei called polar nuclei fused together

80
Q

Central cell consists of

A

2 fused polar nuclei

81
Q

Micropyle

A

The integuments leave a small opening called the micropyle at one end for the entry of pollen tube

82
Q

Each ovule has…

A

1 or 2 protective coverings the integuments
The integuments leave a small opening called micropyle at one end for the entry of pollen tube
Enclosed by the integuments is the nucellus a mass of food laden cells
Further inside the nucellus is the embryo sac.
The embryo sac contains 7 cells
3 cells at micropylar end - 1 egg cell and 2 synergids
3 cells at opposite end called antipodal cells
1 large central cell containing 2 polar nuclei fused together

83
Q

What happens if the pollen grain falls onto the stigma of a different plant species

A

If disintegrates

84
Q

What happens to pollen grain upon falling on atigma

A

It is stimulated to germinate due to the secretion of sugars by the stigma.

85
Q

How does the stigma stimulate the pollen grain to germinate

A

By secreting sugars

86
Q

How does pollen tube grow

A

Through a point in the exine a pollen tube grows out of the pollen grain, carrying the generate nucleus and the tube nucleus at the tip.

87
Q

The generative nucleus divides into

A

2 sperm nuclei

88
Q

Sperm nuclei aka

A

Male gamete nuclei

89
Q

In the terminating pollen grain how many nuclei are there

A

3 nuclei not separated by cell walls and sharing common cytoplasm

90
Q

How does pollen tube grow through stigma and style

A

By dissolving tissues with help of enzymes

91
Q

What happens when pollen tube reaches ovary

A

It pushes through the micropyle and reaches the embryo sac. The tube nucleus which had directed the growth of pollen tube all the way down now disintegrates.

92
Q

What happens when pollen grain enters one of the synergids.

A

It releases its 2 sperm nuclei
Of these 1 sperm nucleus fuses with egg cell nucleus to form zygote
Other sperm nucleus moves towards the two polar nuclei in the central cell and fuses with them and he ce 2 nuclei fused together/triple fusion to produce endosperm occurs
All together 2 fertilizations occur and hence the whole process is termed double fertilization.

93
Q

Triple fusion

A

When pollen tube enters one of the synergids and releases 2 sperm nuclei one moves towards polar nuclei in the central cell and fuses with them and thus 3 nuclei fuse together and triple fusion to produce the endosperm occurs.
The whole process is termed double fertilization.

94
Q

Double fertilization

A

when pollen tube enters one of the synergids it releases its two sperm nuclei.
One fuses with egg cell nucleus to form zygote
Next moves towards the two polar nuclei in the central cell and fuses with them (this 3 nuclei fuse together/triple fusion occurs to produce the
endosperm nucleus).
All together 2 fertilizations hv occurred hence the name double fertilization.

95
Q

What happens to petals after fertilization

A

Falls off

96
Q

What happens to style and stigma after fertilization

A

Falls off

97
Q

Calyx after fertilization

A

Falls off or remains intact in dried shrivelled form
Eg guava apple
Brinjal green calyx persists

98
Q

Stigma after fertilization

A

Falls off

99
Q

Ovary after fertilization

A

Enlarges to form fruit

100
Q

Ovules after fertilization

A

Seeds

101
Q

Ovarian wall after fertilization

A

Pericarp (fruit wall)

102
Q

Placenta after fertilization

A

Stalk of seed

103
Q

Outer integument after fertilization

A

Testa

104
Q

Inner integument after fertilization

A

Tegmen

105
Q

Testa + tegmen fate

A

Seed coat

106
Q

Secondary nucleus fate

A

Endosperm

107
Q

Egg cell + synergids fate

A

Embryo

108
Q

Antipodal cells fate

A

Disorganised

Biology (4 decks)

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