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Trinity Term 1 > The unique reproductive biology of angiosperms > Flashcards

The unique reproductive biology of angiosperms Flashcards

1
Q

Describe the life cycle of a fern

A
  • sorus on pinna protected by indusium
  • sporangium contains spore mother cells (undergo meiosis)
  • produces spores which germinate into gametophyte prothallus (has rhizoids)
  • antheridium produces sperm which disperse to the egg-containing archegonium
  • fertilisation
  • rhizome arms adventitious roots
  • young sporophyte produces fiddleheads
  • frond formation
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2
Q

Fiddleheads

A

furled fronds of a young fern

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3
Q

Give a heterosporous spermatophyte

A

Pinus sylvestris

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4
Q

What is the ovule

A

Megagametophyte enclosed by integument and nucellus

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5
Q

Describe gymnosperms

A
  • mostly monoecious
  • some dioecious
  • unisexual cones
  • most anemophilous
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6
Q

Describe angiosperms

A
  • mostly hermaphroditic (co-sexual flowers)
  • few monoecious or dioecious
  • mostly entomophilous
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7
Q

Describe the Androecium

A
  • stamens
  • contain anther and filament
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8
Q

anther

A
  • 4 loculi
  • contains microsporangium
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9
Q

Describe the pollen grain

A
  • bicellular or tricellular
  • generative cell and vegetative cell nucleus
  • sperm cells and vegetative cel nucleus
  • pollen wall
  • colpus
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10
Q

Describe the pollen wall

A
  • intine
  • foot layer
  • columella
  • tectum
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11
Q

colpus

A
  • groove
  • pl. colpi
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12
Q

Describe the Gynoecium

A
  • carpel and pistil
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13
Q

Apocarpous

A

carpels free

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14
Q

Syncarpous

A

carpels ‘fused’

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15
Q

Connate

A

carpels ‘united’

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16
Q

embryo sac

A
  • megagametophyte
  • 2 integuments
  • micropyle
  • 2 synergids
  • egg cell
  • 2 central cell nuclei
  • 3 antipodal cells
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17
Q

antipodal cells

A

embryo nutrition

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18
Q

synergids

A

cessation of pollen tube growth and release of the sperm cells

19
Q

Describe pollination and double fertilisation - the basics

A
  • pollen tube delivers the two sperm cells to the embryo sac
  • haploid microgametophyte and diploid megasporophyte
20
Q

Describe pollination and double fertilisation - the specifics

A
  • pollen shed from anther and transferred to stigma
  • pollen hydrated on stigma
  • pollen germination and tube growth down style
  • pollen tube grows down transmitting tract to ovary
  • enters micropyle
  • double fertilisation occurs
21
Q

Describe the pre-zygotic events

A
  1. Pollen capture
  2. Pollen adhesion
  3. Pollen hydration
  4. Pollen germination
  5. Pollen tube penetration
    of the stigma
  6. Growth of pollen tube
    towards the ovule
  7. Entry of pollen tube
    into the ovule leading to fertilization
22
Q

What are the implications of the pollen-pistil interaction?

A
  • evolution of pollen discrimination systems
  • pollen competition
23
Q

Describe pollen discrimination systems

A

incompatibility systems

24
Q

SI

A

self-incompatibility

25
Q

List some incompatibility systems

A
  • intra-specific SI systems
  • interspecific incompatibility
26
Q

List some incompatibility systems

A
  • intra-specific SI systems
  • interspecific incompatibility
27
Q

Describe pollen competition

A
  • gametophytic selection
  • vigorous microgametophytes produce fitter offspring.
  • 60-80% of genes expressed in microgametophyte are also expressed in sporophyte: subject to selection during pollen-pistil interaction.
28
Q

Chemical signalling in the pollen tube

A
  • gradient of water potential created by surface lipids of stigma (or pollen coat)
  • various chemical pollen tube attractants in stigma and style
    3. Synergid peptide signal (LURE) attracts pollen tube to ovule as prelude to fertilization (Higashiyama et al 2001 Science 293: 1480- 1483)
29
Q

List some chemical pollen tube attractants

A
  • TTS Arabinogalactan Glycoprotein
  • GABA
  • Chemocyanin
  • Le-STIG1
30
Q

TTS

A

Transmitting Tissue Specific

31
Q

Le-STIG1

A

cysteine-rich stigma-specific protein 1

32
Q

Describe double fertilisation

A
  • triploid endosperm is 2 maternal and 1 paternal
  • diploid embrue is 1 maternal and 1 paternal
  • both vegetative nucleus and endosperm get fertilised
33
Q

Why is the endosperm ratio 2m:1p

A

critical for seed size

34
Q

Describe nuclear endosperm development

A
  • most common form
  • fertilisation followed by repeated free-nuclear divisions =
  • ‘liquid endosperm’
  • if a cell wall is formed it will form after free-nuclear divisions
35
Q

Describe cellular endosperm development

A
  • fertilisation followed by normal cell divisions with cell- wall formation
36
Q

Describe Helobial endosperm development

A
  • rarest form
  • cell wall is laid down between the first two nuclei, after which one half develops cellular endosperm and half nuclear
37
Q

Give examples of nuclear endosperm development

A

coconuts, cereals and beans

38
Q

Give examples of cellular endosperm development

A

Impatiens, Petunia, Datura

39
Q

Give examples of Helobial endosperm development

A

e.g. Asphodelus, Muscari, Saxifraga, Echium.

40
Q

Describe Gymnosperm seeds

A
  • 30mm
  • food reserves laid down in female gametophyte before fertilisation
41
Q

Describe Angiosperm seeds

A
  • 2mm
  • food reserves laid down in endosperm after fertilisation
  • more efficient
42
Q

Describe fruit derivation

A
  • from various parts of the flower
  • ripening swollen ovary
43
Q

Fleshy fruits are

A

an adaptation to entomophilous seed dispersal

Trinity Term 1 (38 decks)

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