Reproductive Biology - Plant Animal Interaction
Transcript of Reproductive Biology - Plant Animal Interaction
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Plant Reproductive Biology
Plant animal interaction
What is pollination?
The transfer of pollen from the male anther tothe female stigma
Why is pollination important? Sexual reproduction
important for evolution
produces variable offspring, creating diversity and variationamong populations (shuffling of genes) for NaturalSelection to occur
advantageous to an organism only if it happens withsomeone other than itself!
Outbreeding good
inbreeding >>>>> homozygous plants
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Path in
pollination
process
Inbreeding
1. autogamy (in the same flower) &
2. geitonogamy (between flowers in one individu)
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
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Strategies to avoid self-pollination
Perfect flowers have both male and femaleorgans, so plants have strategies to avoid self-pollination Outbreeding = outcrossing /allogamy / xenogamy1. Timing male and female structures mature at
different times
2. Morphological structure of male and femaleorgans prevents self-pollination (imperfect flower,heterostily)
3. Biochemical chemical on surface of pollen andstigma/style that prevent pollen tube germinationon the same flower (incompatible)
Difference in timing of floral parts = dichogamy
1. protandry - male first
2. protogyny - female first
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Morphology
Spatial separation of anthers and stigmas =hercogamy, heterostyly
Tristyly
Other mechanisms used by bisexual flowersto avoid self-fertilization:
Genetic self-incompatibility S-genes
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self-incompatibility SSI sporophytic self
incompatibility outcome of pollen tube and style
interactions determined by thegenotype of diploid sporophyte thatproduced the pollen
pollen tube growth arrested onsurface of stigma
S-allele produced before completionof meiosis
GSI - Gametophytic SI outcome of pollen tube and style
interaction determined by thegenotype of the pollen itself
pollen tube growth arrested in thestyle
S-allel produced after meiosis
How do plants get pollen from one plant to another?
Plants are rooted in the groundmust use different strategies:
WIND POLLINATION:
Gymnosperms andsome flowering plants (grasses,trees) use wind pollination.
Flowers are small, groupedtogether not efficient (too chancyand wasteful)
flowers small, numerous, oftenunisexual
perianth absent or non-showy
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Gymnosperms rely on wind to move pollenfrom male to female cones
The ovule exudes sap to trap pollen
Angiosperms have formed many partnerships
with animals to move their pollen
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Co-evolution
Animal plant partnerships are the best known casesof co-evolution: mutual evolutionary influence
Co-evolution interactions between two differentspecies as selective forces on each other, resulting inadaptations that increase their interdependency.
Animal-flowering plant interaction is a classic example
of coevolution:1. Plants evolve elaborate methods to attract animal
pollinators
2. Animals evolved specialized body parts and behaviors thataid plant pollination
Figs and fig wasps
Some flowers provide nurseries for their pollinatorsoffspring
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Why do animals pollinate plants?
Pollinator will get a REWARD: food! In exchange for
moving their pollen to another flower
Nectar a sugary solution produced in specialflower glands called nectariesNectar concentration matches energy requirements of
the pollinator: bird- and bee-pollinated flowers have
different sugar conc. Pollen is high in protein, some bees and beetles
eat it.Flowers can produce two kinds of pollen: a normal
and a sterile, but tasty, kind, for the insect.
Nectary gland
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Definition Nectaries are structure thatusually located within the
base of the flower (floral
nectaries) or on other
portions of the plant
(extrafloral nectaries)
A multicellular glandularstructure secreting nectar.
Found in flowers and onvegetative parts in some
species ofplants, often
forming projections, lobes, or
disk-like structures.
Floral Nectar
The sweet fluid used to attract insect pollinators. Thecomposition of nectar varies among plant species.
Floral glands produce nectar which is energy-rich foodfor animal pollinators. Pollinator visits flower due toattracted showy petals (visual attractant) or scent
(olfactory attractant) The secretion of nectar is usually under developmental
control beginning when the flowers open.
After pollination, the nectar is frequently resorbed
Nectar secretion increases as the flower is visited bypollinators
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Floral nectar in Petunia and Nicotiana
Some flowers provide food (e.g., nectar or pollen) to
their pollinators
Honey beecollecting pollen
and nectar
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Some flowers provide food (e.g., nectar or pollen) totheir pollinators
Kigelia africana
sausage tree
Night Blooming Cirrus
Nectar is usually presented together with
attractive structures, e.g., showy petals and
fragrances
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Getting the pollinators attention
Plants advertise their pollen and nectarrewards with
Colors bees see blue, yellow, UV; while birds seered. Bats dont see well, so flowers are white.
Nectar or honey guides a visual guide for
pollinator to locate the reward (pansy flower)Aromas for insects, nectar.
Can also be carrion or dung smell flys
pollination
Ultraviolet patterns
Petals sometimes exploit the sensory
capabilities of pollinators nectary guide
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Wax or resinreward Collected and used by
female bees for nest
construction
Found in Maxillaria andCymbidium; poorly
studied
Maxillaria notylioglossa
Waxy resin
crystals
Oil reward flowers
Oils (triacyl glycerides) produced on surface offlowers, often in specialized glands--
elaiophores.
Oils are collected by female anthophorid bees;
used to provision nest (food for larvae)
Many orchids mimic Malpighiaceae
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CyrtochilumWith oil gland (elaiophore)
Scents
Insects have great sense of smell may bepleasant or foul to humans but not to insect
Carrion flower smells like rotten flesh andattract flies (ex. Rafflesia)
flies lay eggs, pick up pollen and move on to nextflower looking to lay more eggs and spreadingpollen
eggs never survive as it isnt really poop
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carrion
maroon / brown in color, foul smelling (like rotting flesh)
Plant Mimicry
Some plants take advantage of the sex drive of certaininsects
floral fragrance mimicry of sexual pheromones ofpollinators
Usually visual, tactile mimicry, too Has evolved repeatedly in several different orchid groups
Certain orchids look like female wasps, and even smell likethem!
Males try to mate with them, and in the process they pollinatethe plant
The orchid gets pollinated, but the male wasp onlygets frustrated!
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Some flowers trick their
pollinators
Bucket Orchid
Some flowers trick their pollinators
Bee Orchid
Calochilus paludosa