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biology > Lecture 23 - Plant Reproduction > Flashcards

Lecture 23 - Plant Reproduction Flashcards

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1
Q

What are the 3 “F’s” for Angiosperms?

A
  • Flowers
  • double Fertilization
  • Fruits
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2
Q

What are the 4 whorls of floral organs that flowers are composed of?

A
  • Carpels
  • Stamens
  • Petals
  • Sepals
  • All whorls attached by a receptacle
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3
Q

Carpels

A

megasporophylls composed of stigma, style, ovary

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4
Q

Stamens

A

microsporophylls composed of anthers, filaments

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5
Q

Petals

A

showy, inner whorl

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6
Q

Sepals

A

green (usually), outer whorl

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7
Q

What are all whorls attached by?

A

a receptacle

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8
Q

What are the differences in floral organ numbers?

A
  • complete
  • incomplete
  • inflorescences
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9
Q

What is meant by COMPLETE in terms of differences in floral organ numbers?

A

has all 4 whorls

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10
Q

What is meant by INCOMPLETE in terms of differences in floral organ numbers?

A

missing 1 or more whorls, includes unisexual flowers

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11
Q

Carpellate flower =

A

female only

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12
Q

Staminate flower =

A

male only

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13
Q

What is meant by Inflorescences in terms of differences in floral organ numbers?

A

clusters of flowers (as opposed to a single flower)
• Vary in shape, size, colour, odour, whorl arrangements, time of
opening (ie flowering time)

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14
Q

What do flowers aid in?

A

pollination!

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15
Q

What do wind pollinated flowers do AND what are they the bane of?

A
  • Release lots of smaller pollen grains

* Are the bane of anyone who has seasonal allergies

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16
Q

What happens for animal/insect pollinated flowers?

A
  • Reward the pollinator with food (nectar)

* Many animal pollinators are loyal to the flower species

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17
Q

Many animal pollinators are loyal to the flower species. What will natural selection do, which will inturn result in co-evolution?

A

Natural selection will increase selective pressure for floral traits that make it more prized to the pollinator (more likelihood for pollination)
• The animal pollinator will also evolve to be better able to get the prized nectar
• We call this co-evolution

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18
Q

What is co-evolution?

A

where the pollinator and the pollinatee kind of evolved together, they have the same kind of selective pressures against them, or for them to acquire traits that are going to keep the possibility of pollination high

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19
Q

Sporogenesis

A

development of the mega/micro spores via meiosis

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20
Q

Gametogenesis

A

development of the gametes via mitosis

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21
Q

Describe male gametophytes within pollen grains

A

1) Contained within the anther is the microSPORANGIUM (2n)
2) Within the microsporangium (2n), microsporoCYTES (2n) undergo MEIOSIS to produce microSPORES (n)
3) Each microspore (n) will develop into the POLLEN GRAIN, containing the sporophytic exine (pollen wall) and the male gametophyte (n)
4) The male gametophyte contains the GENERATIVE CELL, which will undergo MITOSIS to produce 2 sperm during pollination, and
5) The tube cell will eventually produce the POLLEN TUBE for fertilisation

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22
Q

What can climate change affect? What can high temperatures induce?

A
  • the viability and fertility of the pollen grains
  • high temperatures can induce apoptosis (programmed cell death) within
    the anthers
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23
Q

Describe female gametophytes (embryo sacs) within megasporangia

A

1) Carpels contain ovules which contain the megaSPORANGIUM (2n)
2) The megasporangium contains the megasporoCYTE (2n), which undergoes meiosis to produce 1 surviving megaSPORE (n)

3) 2 INTEGUMENTS (2n) will develop and surround the ovule, eventually becoming the SEED COAT
• Space between integuments is the microPHYLE

4) The megaspore will undergo MITOSIS 3 times (without cytokinesis)
to produce a 8 nuclei EMBRYO SAC (female gametophyte)

5) The plant hormone AUXIN will determine the fate of each cell in the female gametophyte
6) At the microPYLAR end, 1 egg cell and 2 SYNERGIDS are formed
7) At the opposite end, 3 ANTIPODAL cells are formed (function unknown)
8) The last 2 nuclei become the POLAR NUCLEI, which will be used in endosperm production
* at this point, the ovule now contains the embryo sac enclosed within the megasporangium & the integuments

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24
Q

Describe pollination

A
  • The microsporangium will break open, releasing the pollen grains onto the surface for dispersal
  • The pollen grain is carried to the stigma of the carpel, where it absorbs water and germinates its pollen tube (tube cell does this)
  • As the pollen tube elongates down the style, the generative cell divides by mitosis, producing the two sperm
  • The tube nucleus then carries the two sperm cells through the pollen tube to the female gametophyte (lead by chemicals secreted by the synergids)
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25
Q

Indirect pollination

A

pollen does not land directly on the ovule (angiosperms)

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26
Q

Direct pollination

A

pollen does land directly on the ovule (i.e. gymnosperms)

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27
Q

What happens in Double Fertilization?

A
  • Fertilisation occurs when one of the sperm cells fuses with the egg cell
  • The 2nd sperm continues past the egg cell into the central cell where it combines with the 2 polar nuclei, forming a 3n ENDOSPERM
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28
Q

What does Double Fertilization ensure?

A

that only fertilised ovules have a food supply for the developing embryo

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29
Q

Describe Endosperm Development

A

• After double fertilisation, the triploid (3n) nucleus divides by mitosis into a super cell that has a milky consistency (think coconut “milk”)

• After cytokinesis partitions the nuclei, the endosperm becomes solid
(think coconut “meat”)

30
Q

What is an important food source (popcorn, rice, wheat)?

A

endosperms!

31
Q

Describe Embryo development

A
  • The first mitotic division of the zygote splits the fertilised egg
    • Terminal cell
    • Basal cell

• The terminal cell divides many times and forms the embryo attached
to the suspensor

  • Cotyledons (“first leaves”) begin forming
  • Between the cotyledons are the shoot apex and root apex, which are meristems that will produce the shoots and roots after germination
32
Q

Terminal cell

A

becomes the embryo

33
Q

Basal cell

A

produces a thread of cells called the suspensor, which anchors the embryo to the parent plant & transfers nutrients

34
Q

How many cotyledons do monocots have?

A

1

35
Q

How many cotyledons do eudicots have?

A

2

36
Q

What is the last stage of seed development? AND how much will water content reduct?

A

dehydration!

  • will reduct to 5-15% seed weight
37
Q

The last stage of seed development is dehydration. What does the seed enter?

A

dormancy, where it stops growing & metabolism halts

38
Q

At the last stage of seed development, the seed contains…

A
  • The embryo with its cotyledons and endosperm
  • Hypocotyl
  • Radicle
  • Epicotyl
39
Q

Hypocotyl

A

embryonic axis below the cotyledons

- what the seed contains at the last stage of seed development

40
Q

Radicle

A

embryonic root

- what the seed contains at the last stage of seed development

41
Q

Epicotyl

A

embryonic axis above the cotyledons

- what the seed contains at the last stage of seed development

42
Q

Monocot seeds have only 1 cotyledon but also have…

A
  • Coleoptile

* Coleorhiza

43
Q

Coleoptile

A

protective sheath surrounding the shoot

- what monocot seeds have

44
Q

Coleorhiza

A

protective sheath surrounding the root

- what monocot seeds have

45
Q

How does Germination occur?

A

when water is taken up into the seed (imbibition) due to the low water potential of the dry seed

46
Q

What does Germination cause? AND what happens to the endosperm?

A
  • Causes rapid swelling of the seed, rupturing the seed coat and triggering metabolism
  • Endosperm is digested and transferred to the growing embryo
47
Q

Fruits contain…
AND
are the result of…

A

Fruits contain the seeds and are the result of the ovary swelling
• Ie. Ovules -> seeds, flowers -> fruits

48
Q

The ovary becomes the…

A

pericarp (thickened wall)

49
Q

What are the variety of forms fruits come in?

A
  • simple fruit
  • aggregate fruit
  • multiple fruit
  • accessory fruit
50
Q

Simple fruit

A

derived from a single carpel or fused carpels (ie. Most fruits)

51
Q

Aggregate fruit

A

from a single flower, with each carpel forming a fruit (ex. Raspberries)

52
Q

Multiple fruit

A

develops from a cluster of flowers that fuse together (ex. Pineapples)

53
Q

Accessory fruit

A

fruit formed from other floral parts that are not the carpels (ex. Apples and strawberries)

54
Q

In asexual reproduction…

A

offspring are derived from the parent plant without fusion of an egg + sperm

55
Q

Fragmentation

A

pieces can regenerate into a whole plant (asexual reproduction)

56
Q

Apomixis

A

development of seeds without fertilisation (ex dandelions…..cloning with dispersal!)

57
Q

Types of asexual reproduction

A
  • Fragmentation -> pieces can regenerate into a whole plant
  • Adventitious plantlets (ex Kalanchoe, “Mother of Thousands”, spider plants)
  • Splitting of the root mass/ball (can do this with shrubs, Aspens)
  • Apomixis -> development of seeds without fertilisation (ex dandelions…..cloning with dispersal!)
58
Q

Advantages of asexual reproduction

A
  • Don’t need a pollinator
  • Passes on all its genes to its offspring
  • Vegetative reproduction
59
Q

Disadvantages of asexual reproduction

A
  • No genetic variation
  • Not as long-distant dispersal
  • No seed dormancy
60
Q

What is vegetative reproduction?

A

Food sources from the parent, so more rapid growth compared to sexually formed embryo

61
Q

What does “selfing” allow for?

A

“Selfing” allows for sexual reproduction in plants where pollinators may be scare

62
Q

What does “selfing” risk AND what is it desirable for?

A
  • Risk having weaker (less fit) offspring

* Desirable in crop plants though since each ovule can be fertilised to produce a seed

63
Q

What are the many mechanisms to prevent selfing?

A
  • Plants can be dioecious (i.e. unisexual) with either staminate flowers (male) or carpellate flowers (female)
  • Differences in maturation TIME between stamens and carpels on the same flower
  • Self-incompatibility
  • Based on S-genes
  • Flower structure and arrangement of stamens and carpels
  • Pin flower
  • Thrum flower
64
Q

Self-incompatibility

A

rejects its own pollen
• Based on S-genes -> if the specific allelic combination of S alleles in the pollen match the S alleles of the stigma, it is rejected

65
Q

Pin flower

A

Long styles, short stamens

66
Q

Thrum flower

A

Long stamens, short styles

67
Q

In gymnosperms, seeds are…

A

on ovulate cones as a result of direct fertilisation

68
Q

In gymnosperms, dispersal is likely by…

A

wind (bracts helicopter away from parent tree once cone opens)

69
Q

In angiosperms, seeds are…

A

within fruits as a result of indirect fertilisation

70
Q

In angiosperms, dispersal is due to..

A

a variety of means
• Animals -> dogs with burrs, eating and digestion by animals
• Wind -> winged seeds of maple seeds, dandelion seeds, tumbleweeds
• Water -> coconut and other buoyant seeds

biology (25 decks)

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