The unique reproductive biology of angiosperms Flashcards
(43 cards)
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
2
Q
Fiddleheads
A
furled fronds of a young fern
3
Q
Give a heterosporous spermatophyte
A
Pinus sylvestris
4
Q
What is the ovule
A
Megagametophyte enclosed by integument and nucellus
5
Q
Describe gymnosperms
A
- mostly monoecious
- some dioecious
- unisexual cones
- most anemophilous
6
Q
Describe angiosperms
A
- mostly hermaphroditic (co-sexual flowers)
- few monoecious or dioecious
- mostly entomophilous
7
Q
Describe the Androecium
A
- stamens
- contain anther and filament
8
Q
anther
A
- 4 loculi
- contains microsporangium
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
10
Q
Describe the pollen wall
A
- intine
- foot layer
- columella
- tectum
11
Q
colpus
A
- groove
- pl. colpi
12
Q
Describe the Gynoecium
A
- carpel and pistil
13
Q
Apocarpous
A
carpels free
14
Q
Syncarpous
A
carpels ‘fused’
15
Q
Connate
A
carpels ‘united’
16
Q
embryo sac
A
- megagametophyte
- 2 integuments
- micropyle
- 2 synergids
- egg cell
- 2 central cell nuclei
- 3 antipodal cells
17
Q
antipodal cells
A
embryo nutrition
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
- Pollen capture
- Pollen adhesion
- Pollen hydration
- Pollen germination
- Pollen tube penetration
of the stigma - Growth of pollen tube
towards the ovule - 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
List some incompatibility systems
- intra-specific SI systems
- interspecific incompatibility
26
List some incompatibility systems
- intra-specific SI systems
- interspecific incompatibility
27
Describe pollen competition
- 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
Chemical signalling in the pollen tube
- 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
List some chemical pollen tube attractants
- TTS Arabinogalactan Glycoprotein
- GABA
- Chemocyanin
- Le-STIG1
30
TTS
Transmitting Tissue Specific
31
Le-STIG1
cysteine-rich stigma-specific protein 1
32
Describe double fertilisation
- triploid endosperm is 2 maternal and 1 paternal
- diploid embrue is 1 maternal and 1 paternal
- both vegetative nucleus and endosperm get fertilised
33
Why is the endosperm ratio 2m:1p
critical for seed size
34
Describe nuclear endosperm development
- 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
Describe cellular endosperm development
- fertilisation followed by normal cell divisions with cell- wall formation
36
Describe Helobial endosperm development
- rarest form
- cell wall is laid down between the first two nuclei, after which one half develops cellular endosperm and half nuclear
37
Give examples of nuclear endosperm development
coconuts, cereals and beans
38
Give examples of cellular endosperm development
Impatiens, Petunia, Datura
39
Give examples of Helobial endosperm development
e.g. Asphodelus, Muscari, Saxifraga, Echium.
40
Describe Gymnosperm seeds
- 30mm
- food reserves laid down in female gametophyte before fertilisation
41
Describe Angiosperm seeds
- 2mm
- food reserves laid down in endosperm after fertilisation
- more efficient
42
Describe fruit derivation
- from various parts of the flower
- ripening swollen ovary
43
Fleshy fruits are
an adaptation to entomophilous seed dispersal
