Transcript Plant Reproductive Biology

Plant Reproductive Biology
Michael G. Simpson
What is it?
Study of sexual and asexual reproduction
Pollination mechanisms
Gene flow
Genetic variation
Propagule dispersal
Why study it?
Insight into adaptive significance & homology of systematic
characters
Insight into delimitation of species and subspecies.
Sexual Reproduction
Non-seed plants
Seed plants:
Pollination - transfer of pollen from microsporangia to
stigma (angiosperms) or ovule (gymnosperms)
Wind pollination - ancestral (all gymnosperms)
Animal pollination - derived for angiosperms
Some angiosperms secondarily wind pollinated
Fertilization - fusion of sperm and egg ––> embryo (new
sporophyte)
Strategy of animal pollination:
Attractant & Reward
Attractant
Visual
perianth
stamens (e.g., Myrtaceae, Mimosoideae)
staminodes (e.g., Zingiberaceae, Cannaceae)
corona (e.g., Narcissus)
inflorescence
Olfactory - usu. from perianth
sweet
rotten (foul/fetid) - e.g., fly pollinated flowers
Strategy of animal pollination:
Attractant & Reward
Reward
Nectar
Pollen
Waxes
Resins
or “Trick” instead of a “Treat”
Insect trapped (Aristolochia) or drowned (Nymphaea sp.)
Mimicry
E.g., fooling male insect into “mating” with orchid
Pollination Mechanisms
INSECT (entomophily)
Bees (melittophily/hymenopterophyly):
fls. showy, colorful, fragrant, with:
nectar guides
landing platforms
Butterflies (psychophily):
fls showy, colorful, fragrant
no nectar guides
long tubes or spurs
Pollination Mechanisms
Moths (phalaenophily):
large, white, fragrant
no nectar guides
usually tubes or spurs
Pollination Mechanisms
Flies (sapromyiophily)
maroon / brown in color
foul smelling (like rotting flesh)
Pollination Mechanisms
Birds (ornithophily):
red (often, not always)
tubular (often)
Pollination Mechanisms
Bats (cheiropterophily):
nocturnal anthesis
large, colorful or white
produce copious nectar or pollen
Pollination Mechanisms
Wind (anemophily):
flowers small, numerous, often unisexual
perianth absent or non-showy
flowers often produced in mass
Pollination Mechanisms
Water (hydrophily):
Breeding systems
Outbreeding versus Inbreeding vs. in-between
Breeding systems
Outbreeding = outcrossing / allogamy / xenogamy:
How is it promoted?
1) Plant sex: dioecy (incl. gynodioecy, androdioecy, trioecy)
Breeding systems
Outbreeding = outcrossing / allogamy / xenogamy:
2) Difference in timing of floral parts = dichogamy
protandry - male first
protogyny - female first
Breeding systems
Outbreeding = outcrossing / allogamy / xenogamy:
3) Spatial separation of anthers and stigmas = hercogamy
heterostyly: different style/stigma & correlated anther heights
Outbreeding = outcrossing / allogamy / xenogamy:
3) Spatial separation of anthers and stigmas = hercogamy
enantiostyly: left & right-handed flowers
Outbreeding = outcrossing / allogamy / xenogamy:
3) Spatial separation of anthers and stigmas = hercogamy
movement hercogamy: trigger mechanisms
Outbreeding = outcrossing / allogamy / xenogamy:
3) Spatial separation of anthers and stigmas = hercogamy
movement hercogamy: e.g., stigma movement
Diplacus [Mimulus] aurantiacus (Phyrmaceae)
Folding of style best explained as adaptation
to reduce interference in bird pollination
Outbreeding = outcrossing / allogamy / xenogamy:
4) Self-incompatibility
Genetically determined, inability for fertilization to occur between
gametes derived from one individual.
Inbreeding = selfing
autogamy (w/in 1 flower) & geitonogamy (between fls. of 1 indiv.)
Selective advantage: ensures propagule production
Disadvantage: reduced to absent genetic variability
allautogamy: both outcrossing & inbreeding
e.g., Viola, Clarkia: two flower types:
chasmogamous flowers - normal, open
cleistogamous flowers - remain closed
Fruit/seed dispersal
Wind - samaras, winged seeds
Water - e. g., Cocos nucifera (Arecaceae)
Explosive dehiscence
Self (Autochory, e. g., Arachis hypogaea)
Animal
Asexual Reproduction
Vegetative reproduction: ramets
Rhizomes
Bulbs, bulbels
Corms, cormels
Plantlets
Asexual Reproduction
Agamospermy - seed production without fertilization
Parthenogenesis (diploid egg)
Adventive polyembryony (non-egg diploid cell)
Hybridization in plants
Polyploidy – evolution of multiple sets of chromosomes; major
mechanism of speciation.
Hybridization in plants
Common
Can produce sterile, vegetatively reproducing species (e. g.,
certain cacti)
Testing for breeding mechanisms
1) Control
2) Caged, self-pollinated
3) Caged, left alone
4) Emasculated, caged
5) Caged, emascul., outcrossed
A
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B
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C
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D
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What is the breeding mechanisms for
species A, B, C, D?