Exam 4
Seeds, Orgins
Microgametophytes
Flowers/ Orgins
Seed plants
Seed ferns (extinct)
Gymnosperms
Progymnosperms (extinct)
Angiosperms
Orgins
Earliest seed
Elkinsia polymorpha
4-5 lobes fused basal third
~360mya
Late Devonian (W. Virginia)
Pseudosporogonites quadrapartitus
Primitive ovule
Lobate integuments
Free from nucellus/ megasporangium
Moresnetia zalesskyi
8-10 lobes fused at chalaza and widely separated
~360mya
Ovule evolution
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Evolved from shoot apex
Gymnosperm nucellus apex similar to shoot apex
Similar genes
Innovations
Heterospory
Protection
Integuments
Pollen capture
Pollen chamber
Micropyle
Nucellus
Evolution of the ovule
#
Heterospory
Megasporangium enclosed in integuments
Retention of megaspores w/in megasporangium
Reduction # of megasporocytes/ megasporangium to 1
Survival of 1 megaspore
Endosporic megagametophyte
Modification of megasporangium apex for microspores or microgametophytes
Embryo develop within megagametophyte
Heterospory
Megaspores
Megagametophyte
Microspores
Microgametophyte
Found in some non-seed plants
Megasporangium enclosed in integuments
First integument telomes
Second integument phyllad origin
Reduce # of megasporocytes/ megasporangium to 1
click to edit
Megasporocyte
Megaspore mother cell
Reduced to one per megasporangium rather than hundreds
Survival of 1 megaspore
Megasporocyte undergoes meiosis
4 resulting daughter cells
3 megaspores degenerate
1 megaspore remains
Retention of megaspores w/in megasporangium
Reduced megaspores with other 3 aborted
Large megaspore retained inside megasporangium
Extra layer of protection
Endosporic megagametophyte
Megagametophyte retained inside megaspore wall
Fertilization of egg occurs in wall
Extra layer of protection
Modification of megasporangium apex
Pollen chamber
Through programmed cell death
Micropyle
Embryo develop within megagametophyte
Multicellular megagametophyte
Egg retained
After syngamy, embryo develops within
Multicellular free
Gametophyte dominant stage in early land plants
Reduced over time
Antheridia
Sperm development within antheridia
Sperm rely on water for swimming to archegonia
Flagellated sperm
Pollen
Microgametophyte
Dispersal no longer requires water
Exine prevents desiccation
Some with air bladders
Transport by wind
Haustoria pollen tubes
Tubes feeding on nucellus
Provide nutrients to developing sperm
Can be a lengthy process from pollination to fertilization
Direct delivery
Direct delivery of sperm to the megagametophyte
Pollen tube
Directed by synergids
Feeds on nucellus (gymnosperm)
Feeds on style (angiosperm)
Reduced
Angiosperm, 3-celled
Tube cell
Generative cell
Microspore within microsporangium
Mitosis within microspore wall
Endosporic male gametophyte = pollen grain
Ovule diversity
Gymnosperm
Megasporangium is nutritious tissue = nucellus
Nested doll
Integument (1)
Megaspore wall
Megasporangium
Archegonium
Eggs
Example: Pine Ovule
Ovule on megasporophyll
1 microsporocyte
Pollen chamber
Nesting doll
Integument
Nucellus
Megaspore wall
Megagametophyte
Archegonium
Egg
Angiosperm ovule
2 integuments
Megasporangium = nucellus
Megasporocyte reduced to one
Megaspore reduced to one and retained
Megagametophyte = egg sac
Furniculum
Example: Lily Ovule
1 megasporocyte
1 megaspore
2 integuments
Embryo sac = megagametophyte
8 nucleate
3 antipodals
Sometimes nutritive
2 polar
Becomes endosperm
2 synergids
Guide pollen tube
1 egg
Eventual zygote
Gymnosperm vs Angiosperm
Both single megasporocyte
Both single megaspore
1 integument, 2 integuments
Unique to Angiosperm
Additional protection from ovary wall
Double fertilization
Seeds
Advantages
Enabled colonization of drier upland habitats
Enabling advanced reproductive traits
Pollination drops
Embryo dormancy increase chance of offspring survival
Increased independence from free water reproduction
Gymnosperm
Pine example
Some with fleshy outer layer (aril)
Several cotyledons
Integument becomes seed coat
Double-fertilization
#
Pollen tube grows down style
Generative cell divides into 2 sperm
Pollen tube ruptures inside synergid releasing sperm
One sperm fuses with egg
2n diploid
Zygote
One sperm fuses with polar nuclei
3n triploid
Endosperm
Monocot
One cotyledon = scutellum
Large amount of endosperm
Corn example
Integuments become seed coat
eudicot
2 cotyledons
Large amount of endosperm
Integuments become seed coat
Bean example
STEPS
Ancestral flower
Based on molecular data
Bisexual
Radially symmetric
Multiple whorls of petals
Androecium
2+ whorls of anthers
Gynoecium
5+ carpels
First flower fossil
Archaefructus sinensis
Likely herbaceous
Likely aquatic
124.6bya
Most primitive extant
Amborellaceae
Amborella
Amborella trichopoda
New Caledonia
Dioecious
Male plants
Female plants
Shrub
General trends
Flowers indefinite in number of parts →flowers have few parts that are definite in number
Floral axis shortened
Original spiral arrange no longer evident
Floral parts often fused
Ovary superior → inferior
Perianth has become differentiated in distinct calyx & corolla
Radial symmetry →irregularity
Basic Structure
Perfect, complete flower
#
A flower is a stem with leaf-like structures.
Complete flowers have all four floral appendages:
Sepals, sterile
Petals, sterile
Stamens, male fx
Carpels, female fx
Incomplete flowers lack at least one appendage
Sepals
#
Sepals are the outermost floral appendage.
Are modified leaves that surround maturing flower parts.
Protect the flower bud as it develops.
May be colorful.
All the sepals together are referred to as the calyx.
Petals
#
Petals are located above the sepals on the receptacle.
Are leaf-like but contain pigments other than chlorophyll.
Attract pollinators.
Collectively are a corolla.
Sepals and petals collectively are a perianth.
Absent in wind-pollinated species.
Stamens
#
Stamens occur above the petals.
Are collectively the androecium.
Two parts: anther and its supporting filament.
Diploid anther cells (microsporocytes) undergo meiosis to produce four microspores.
Microspores
Undergo mitosis
form a resistant cell wall
Microgametophyte
Pollen grains
Megasporophyll
Carpels, collectively, are the gynoecium.
Stigma catches pollen grains.
Style elevates the stigma.
Ovary where megaspores are produced.
Within the ovary are placentae bearing small structures called ovules
After fertilization of the egg, ovules mature into seeds.
Structure modifications/ Flowers
Carpel position
Whorls inserted relative to ovary
Superior
Carpel above
Inferior
Receptacle surrounds carpel
Carpel below
Perianth & stamen insertion
Hypogynous
Perianth & stamens on receptacle beneath ovary
ex lilies
Epigynous
Perianth & stamens from top of ovary
ex apple flower
Perigynous
Perianth & stamens adnate to calyx
ex cherry flower
Imperfect flowers
Lacking a whorl of sexual organs
Hermaphroditic = perfect
Monoecious = male flowers and female flowers on the same plant
Dioecious = male flowers on plant, female flowers on different plant
Male = androecious
Female = gynoecious
Display variation
Inflorescence
Taxonomic importance
Various ways to ensure cross pollination
Pollination syndromes: trait modifications
Major traits
#
Color
Smell, organic volatiles
Shape
Bloom time
Rewards, eg nectar
colors
Some colors are more attractive than others
Color requires resource
Omit when unnecessary
Some are in the uv spectrum
Scent
Signal to pollinators
Sometimes use own preferences and sexual pheremones
Some common chemicals
Benzaldehyde (almond)
Linalool (lavender)
Limonene (citrus)
Beta ocimene (green)
May have scent glands
eg roses
Shape
Floral symmetry
Actinomorphic
Radially symmetric
eg sunflower
Zygomorphic
Irregular
Bilateral
eg pea
Blooming time
Diurnal
Day time
Nocturnal
Night time
Rewards
Nectar
Pollen
Oil
Pollination syndromes: types
#
Major syndromes
Abiotic:
Anemophily (wind)
Hydrophily (water)
Biotic
Melittophily (bee)
Psychophily (butterfly)
Phalenophily (moth)
Myophily, sapromyophily (fly)
Ornithophily (bird)
Chiropterophily (bat)
Cantharophily (beetle)
Anemophily
Wind
No bright colors, special odors, or nectar
Small
Most have no petals
Stamens and stigmas exposed to air currents
Large amount of pollen
Pollen smooth, light, easily airborne
Stigma feathery to catch pollen from wind
Hydrophily
Water
Copious pollen
Small flowers
Long filaments for pollen transport on surface
Oblong, heavier pollen for submarine transport
Melittophily
Bee
Full of nectar
Brightly colored with petals that are usually blue or yellow or a mixture of these (bees cannot see red) but can in UV
Sweetly aromatic or have a minty fragrance
Open in daytime
Provide landing platforms
Often bilaterally symmetrical (one side of the flower is a mirror image of the other)
Flowers are often tubular with nectar at base of tube
Psychophily
Butterfly
In clusters and provide landing platforms
Brightly colored (red, yellow, orange)
Open during the day
Ample nectar producers, with nectar deeply hidden
Nectar guides present
May be clusters of small flowers (goldenrods, Spirea)
Phaelonophily
Moth
Many night pollinated species
White
Heavy scent
Tubular corollas
Myophily
Fly
Pale and dull to dark brown or purple
Sometimes flecked with translucent patches
Putrid order, like rotting meat , carrion, dung, humus, sap and blood
Nectar guides not present
Produce pollen
Flowers are funnel like or complex traps
Saprophily, for carrion mimics
Ornithophily
Bird
Tubular and have petals that are recurved to be out of the way
Have tubes, funnels, cups
Strong supports for perching
Brightly colored: red, yellow, or orange
Odorless (birds have a poor sense of smell)
Open during the day
Prolific nectar producers with nectar deeply hidden
Modest pollen producers that are designed to dust the bird’s head/back with pollen as the bird forages for nectar
Chiropterophily
Bat
Open at night;
Large in size (1 to 3.5 inches);
Pale or white in color;
Very fragrant, a fermenting or fruit-like odor; and/or
Copious dilute nectar.
Cantharophily
Beetle
Bowl-shaped with sexual organs exposed
White, to dull white or green
Strongly fruity
Open during the day
Moderate nectar producers
May be large solitary flowers (i.e. magnolias, pond lilies)
May be clusters of small flowers (goldenrods, Spirea)
Deception
May look like pollinator
May smell like pollinator
Uses trickery
Usually no reward
Saprophily included
Fruits
After double fertilization
Primary endosperm nucleus divides forming endosperm
Zygote develops in embryo
Integuments develop into a seed coat
Ovary wall and related structures develop into fruit
Fruit formation
Ovary sometimes with other portions of flower or inflorescence develops into a fruit
Ovary wall
Pericarp
Thickens and differentiations
Exocarp
Mesocarp
Endocarp
Pericarp
Exocarp
Mesocarp
Endocarp
Accessory fruits
Any fruit with accessory tissue
Tissue besides the ovary is included in the fruit
Can be simple, aggregate or multiple
Parthenocarpic fruits
Fruit development
Without fertilization
Without seed development
Banana
Seedless watermelon
Simple fruits
Single carpel
2+ united carpels
Examples
Bean
Cherry
Tomato
Major fleshy types
Berries
Drupes
Pomes
Major dry types
Dehiscent
Indehiscent
Aggregate fruits
Apocarpous gynoecium
Carpel retains its identify in mature state
Example
Magnolias
Raspberries
Strawberries
Multiple fruits
Derived from an inflorescence
Combined gynoecia of many flowers
Example
Fig
Mulberry
Pineapple
Seed dispersal
Syndromes
Wind
Water
Animal
Active
Passive
Self
Wind
Wings
Parachutes
Lightweight seeds
Water
Buoyant
Large airspaces
Example coconut
Animal, active
Fleshy
Provide animal with nutrients
Long-distance dispersal
Seed pass through gut without harm
Seeds are regurgitated later
Ends up in a nice little pile of nutrient dense excrement
Ants with elaiosome (lipid based nutrient rich)
Animal, passive
Hooks
Catch on fur
Catch on hoof
Velcro
Self
Gravity
Exploding
Gynomoniousous= having hermaphroditic and gynoecious
Andromoniousous= having hermaproditic and androecious
Trimoniousous= having all Three