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Polliniation And Fertilization Flashcards

(108 cards)

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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
Cross pollination advantages
Healthier offsprings Abundant, viable seeds New varieties may be produced by cross pollinating 2 different varieties of same species
26
Cross pollination disadvantages
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.
27
Which type of pollination is favoured by nature
Cross
28
What conditions favour cross pollination
Unisexuality Dichogamy Self sterility Herkogamy Heterostyly
29
Explain dichogamy
When there are different timings of maturation of Androceium and gynoecium.
30
Types of dichogamy
Protandry Protogyny
31
Protoandry + Eg
Anther of flower matures earlier than stigma Lady finger, sweet pea, Salvia, sunflower
32
Protogyny + Eg
The stigma of flower matures eaker than anthers Custard apple Peepal
33
Self sterility
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
34
Self sterility ex
Ray florets of sunflower Orchids
35
Herkogamy + Eg
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
36
Heterostyly + eg
In these the stigma and anthers grow at different heights which does not favour self pollination. Primrose, oxalis
37
4 differences between cross and self pollination
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.
38
Entomophilous
Insect pollinated
39
Characteristics of insect pollinated flower
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
40
Eg of flower in cluster
Dahlia
41
Anemophilous
Wind pollinated
42
Wind pollination characteristics of flowers
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**
43
Eg of wind pollinated flower
Maize
44
Versatile anther
Anther are large loosely attached to filament so slightest wind will move them
45
Hydrophilous
Water pollinated (only in aquatic plants)
46
Characteristics of flowers that are water pollinated
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
When is male flower such that it floats on water surface go meet female flowers
Vallisneria
48
Bird pollination + eg
Ornithophily Bignonia, canna
49
Elephant pollination
Elephophily
50
Anther are large loosely attached to filament so slightest wind will move them
Versatile anther
51
Elephophily example in detail
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
Define artificial pollination
When man himself transfers the pollen grains to the stigma of a flower
53
In which civilisation was artificial pollination popular? Which plant did they do it to?
Ancient babylonia Palm flowers
54
Artificial pollination aka
Artificial croasing
55
Emadculation
Removal of anthers in young flowers for artificial pollination.
56
Bagging
During artificial pollination they remove the anther in young flowers and then cover these flowers with plastic bags (bagging).
57
How is artificial pollination done
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
Why is artificial pollination done
Done by scientists and plant breeders to evolve new varieties.
59
Define fertilization
The union/fusion of the nuclei of the male and female gametes
60
Each pollen grain has how many male gametes
2
61
What produces female gamete
Ovule inside ovary
62
What is the outerwall of pollen
Exine
63
Inner wall of pollen
Intine
64
Nucleus of pollen grain has divided into
Tube nucleus and generative (male) nucleus.
65
The nucleus of pollen grain has _______ been divided
Already
66
Further changes in pollen grain occur only if
If it has fallen on the stigma of a plant of same species.
67
Describe the pollen grain (mature)
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
Inner part of ovary
Ovule
69
Ovary matures to become
Fruit
70
Ovule becomes
Seed
71
How many ovules may be there
Single ovule - producing single seeded fruit Many ovules - producing many seeded fruit
72
Each ovule has one or two protective coverings
Integuments
73
Each ovule has one or two protective coverings
Integuments
74
Integuments have small opening called? What does it facilitate?
Micropyle at one end Entry of pollen tube
75
What is enclosed by integuments
Nucellus
76
What is nucellus
A mass of food laden cells
77
Integuments
Each ovule has one or two protective coverings called integuments
78
Embryo sac is located
Further inside nucellus
79
Embryo sac contains
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
Central cell consists of
2 fused polar nuclei
81
Micropyle
The integuments leave a small opening called the micropyle at one end for the entry of pollen tube
82
Each ovule has...
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
What happens if the pollen grain falls onto the stigma of a different plant species
If disintegrates
84
What happens to pollen grain upon falling on atigma
It is stimulated to germinate due to the secretion of sugars by the stigma.
85
How does the stigma stimulate the pollen grain to germinate
By secreting sugars
86
How does pollen tube grow
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
The generative nucleus divides into
2 sperm nuclei
88
Sperm nuclei aka
Male gamete nuclei
89
In the terminating pollen grain how many nuclei are there
3 nuclei not separated by cell walls and sharing common cytoplasm
90
How does pollen tube grow through stigma and style
By dissolving tissues with help of enzymes
91
What happens when pollen tube reaches ovary
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
What happens when pollen grain enters one of the synergids.
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
Triple fusion
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
Double fertilization
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
What happens to petals after fertilization
Falls off
96
What happens to style and stigma after fertilization
Falls off
97
Calyx after fertilization
Falls off or remains intact in dried shrivelled form Eg guava apple Brinjal green calyx persists
98
Stigma after fertilization
Falls off
99
Ovary after fertilization
Enlarges to form fruit
100
Ovules after fertilization
Seeds
101
Ovarian wall after fertilization
Pericarp (fruit wall)
102
Placenta after fertilization
Stalk of seed
103
Outer integument after fertilization
Testa
104
Inner integument after fertilization
Tegmen
105
Testa + tegmen fate
Seed coat
106
Secondary nucleus fate
Endosperm
107
Egg cell + synergids fate
Embryo
108
Antipodal cells fate
Disorganised

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