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AngiospermAngiospermDevelopmentDevelopment
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EmbryogenesisEmbryogenesis
Establishes Establishes body plan of the body plan of the plantplant Apical-based Apical-based
patternpattern Radial patternRadial pattern
Accompanies Accompanies seed seed developmentdevelopment
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Formation of the EmbryoFormation of the Embryo Early stages same in all angiospermsEarly stages same in all angiosperms
Terminal cell == apical cellTerminal cell == apical cell Basal cell anchors embryo at micropyleBasal cell anchors embryo at micropyle
Polarity!Polarity! Divisions Divisions embryo proper + embryo proper +
suspensorsuspensor
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Primary MeristemsPrimary Meristems ProtodermProtoderm
Periclinal divisions (parallel to surface)Periclinal divisions (parallel to surface) ProcambiunProcambiun Ground meristemGround meristem
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Developmental Developmental StagesStages
Globular stage (e-h) – Globular stage (e-h) – precedes cotyledon precedes cotyledon developmentdevelopment
Globular Stage Globular Stage Heart Heart Stage (i)Stage (i) Monocots – cylindricalMonocots – cylindrical
Torpedo Stage (k-l)Torpedo Stage (k-l) Development becomes Development becomes
restricted to meristemsrestricted to meristems
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SuspensorSuspensor
Supports development of embryo properSupports development of embryo proper Angiosperm suspensors metabolically Angiosperm suspensors metabolically
activeactive Fern and gymnosperm suspensors – push Fern and gymnosperm suspensors – push
embryo into nutritive tissuesembryo into nutritive tissues Angiosperm suspensor – provides embryo Angiosperm suspensor – provides embryo
with nutrients and hormoneswith nutrients and hormones Short-livedShort-lived
Gone by torpedo stageGone by torpedo stage
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ArabidopsisArabidopsis mutants mutants Source of Source of
mutations that mutations that explain plant explain plant developmentdevelopment Expose seed to Expose seed to
mutagenmutagen Mutants produce Mutants produce
seedseed
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B – no apical meristem/cotyledonsC – no hypocotylD – no rootE – no apical and no basal portions
ArabidopsisArabidopsis mutants mutants
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Which Genes Set Up Which Genes Set Up Body Axes?Body Axes?
MONOPTEROSMONOPTEROS -- sets up apical- -- sets up apical-basal axis.basal axis. Codes for MONOPTEROS protein -- Codes for MONOPTEROS protein --
transcription factor.transcription factor.
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Auxin and MonopterosAuxin and Monopteros
Auxin – hormone produced in Auxin – hormone produced in meristemmeristem
Concentration gradient provides Concentration gradient provides positional informationpositional information
Auxin triggers production of Auxin triggers production of regulatory transcription factors regulatory transcription factors specific to cells in the hypocotyl & rootsspecific to cells in the hypocotyl & roots Establishes positional axisEstablishes positional axis
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Mature Embryo & SeedMature Embryo & Seed Embryo continually nourished during Embryo continually nourished during
developmentdevelopment Perisperm (from nucellar tissue) within Perisperm (from nucellar tissue) within
endospermendosperm Cotyledons Cotyledons
Funiculus detaches from ovule Funiculus detaches from ovule nutritionally closed systemnutritionally closed system
Seed dessicatesSeed dessicates Seed coat hardensSeed coat hardens
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Mature EmbryoMature Embryo Axis bearing cotyledonsAxis bearing cotyledons Opposite endsOpposite ends
Shoot apical meristemShoot apical meristem Root apical meristemRoot apical meristem
Epicotyl – stemlike axisEpicotyl – stemlike axis Plumule – embryonic shoot & leavesPlumule – embryonic shoot & leaves
Hypocotyl – stemlike axisHypocotyl – stemlike axis Radicle Radicle
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Endosperm & PerispermEndosperm & Perisperm
Some seeds (e.g., beet) contain both Some seeds (e.g., beet) contain both Endosperm – double fertilizationEndosperm – double fertilization Perisperm – proliferation of nucellusPerisperm – proliferation of nucellus When endosperm absorbed – large When endosperm absorbed – large
cotyledonscotyledons Sunflower, walnut, pea, beanSunflower, walnut, pea, bean
Large amounts of endosperm – Large amounts of endosperm – membranous cotyledonsmembranous cotyledons
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Dicot SeedsDicot Seeds When endosperm absorbed – large When endosperm absorbed – large
cotyledonscotyledons Sunflower, walnut, pea, beanSunflower, walnut, pea, bean
Large amounts of endosperm – Large amounts of endosperm – membranous cotyledonsmembranous cotyledons
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Monocot SeedsMonocot Seeds Grasses – massive cotyledon Grasses – massive cotyledon
scutellumscutellum Both radicle & plumule sheathedBoth radicle & plumule sheathed Coleorhiza and coleoptileColeorhiza and coleoptile
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Seed GerminationSeed Germination Embryo growth delayed while seed maturesEmbryo growth delayed while seed matures Germination – resumption of embryo growthGermination – resumption of embryo growth
Many factorsMany factorso External – water, oxygen and temperatureExternal – water, oxygen and temperature
Mature seeds typically Mature seeds typically drydry Imbibation for enzymatic activityImbibation for enzymatic activity
Cells that produced reserve materials now Cells that produced reserve materials now digestdigest
Cell enlargement & cell divisionCell enlargement & cell division Early germination Early germination anaerobicanaerobic
Once seed coat ruptured – process is aerobic!Once seed coat ruptured – process is aerobic!
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Seed DormancySeed Dormancy
Physiologically immature embryoPhysiologically immature embryo After-ripeningAfter-ripening
Cold periodsCold periods DigestionDigestion FireFire Water Water
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Embryo to AdultEmbryo to Adult First emergent structure – rootFirst emergent structure – root
Anchors plantAnchors plant Absorbs waterAbsorbs water
Primary rootPrimary root Branch or lateral rootsBranch or lateral roots
Adventitious rootsAdventitious roots Shoot-borne rootsShoot-borne roots
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Epigeal & Hypogeal Epigeal & Hypogeal GerminationGermination
EpigealEpigeal HypocotylHypocotyl elongates elongates hook hook Hook straightens Hook straightens pulls cotyledons & pulls cotyledons &
plumuleplumule HypogealHypogeal
Epicotyl Epicotyl elongates elongates hook hook Hook straightens Hook straightens pulls plumule pulls plumule
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EndospermPresent
EndospermAbsorbed into CotyledonsBefore Germination
Epigeous:Cotyledons Emergent
Hypogeous:
Cotyledons Not Emergent
1. Corn(Monocot)
3. Bean(Dicot)
2. Pea(Dicot)
4. Onion(Monocot)
Castor Bean(Dicot)
GerminationStartSeed
Development
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Type 1Type 1 HypogeousHypogeous MonocotMonocot Highly Highly
differentiatdifferentiated embryoed embryo
EndosperEndosperm m absorbed absorbed during during germinatiogerminationn
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Type 2Type 2
HypogeousHypogeous DicotDicot Endosperm Endosperm
absorbed absorbed well well beforebefore germinationgermination
Cotyledons fill Cotyledons fill seedseed
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Type 3Type 3 EpigeousEpigeous DicotDicot Endosperm Endosperm
absorbed absorbed well well before before germinationgermination
Cotyledons fill Cotyledons fill seedseed
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Type 4Type 4
EpigeousEpigeous MonocotMonocot Endosperm Endosperm
absorbed absorbed duringduring germinationgermination
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Type 4Type 4
EpigeousEpigeous DicotDicot Endosperm Endosperm
absorbed absorbed duringduring germinatiogerminationn