Plant Reproduction - Reproduction in Flowering Plants...

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Reproduction in Flowering Plants
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Angiosperm Reproduction Key Concepts Pollination enables gametes to come together in a single flower After fertilization, ovules develop into seeds & ovaries into fruits Many flowering plants clone themselves by asexual reproduction Plant biotechnology is transforming agriculture
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Crops from Seeds Bo th s e xual and as e xual  re pro duc tio n are   im po rtant in ag ric ulture . S e e d g ro wn c ro ps :  whe at, ric e , m ille t and  c o rn s o ybe ans s o ybe an whe at Ric e  plants Bas m ati ric e Japo nic a (s ho rt  g rain) ric e c o ffe e Kidne y  be ans coconuts
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Pollination enables gametes to come together within a flower In angiosperms, the dominant sporophyte Produces spores that develop within flowers into male gametophytes (pollen grains) Produces female gametophytes (embryo sacs) Rafflesia , The “ Monster Flower”
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The Angiosperms: Flowering Plants Stamens – male sex organs, structures bearing microsporangia, composed of filament bearing a two-lobed anther, consisting of four microsporangia fused together. C arpe ls  – fe m ale  s e x o rg ans , s truc ture s  be aring  m e g as po rang ia Pis til  - o ne  o f m o re  fus e d c arpe ls O vary  – s wo lle n bas e  o f c arpe l (o r pis til) c o ntaining    1 e m bryo S tyle  – apic al s talk o f pis til S tig m a  – te rm inal s urfac e  that re c e ive s  po lle n  c arpe l s tam e n C o ro lla ; fo rm e d by  pe tals C alyx : fo rm e d by  s e pals
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Floral Structure Many variations in floral structure have evolved during the 140 million years of angiosperm history Bilateral symmetry (orchid) Sepal Radial symmetry (daffodil) Fused petals Semi-inferior ovary Inferior ovary Superior ovary Lupine inflorescence Sunflower inflorescence Maize, a monoecious species Dioecious Sagittaria latifolia (common arrowhead) REPRODUCTIVE VARIATIONS SYMMETRY OVARY LOCATION FLORAL DISTRIBUTION
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The Control of Organ Identity by Type A, B, and C Homeotic Genes (The ABC Model) The role of the organ identity genes in floral development is dramatically illustrated by experiments in which two or three activities are eliminated by loss-of- function mutations Mutant plants lacking all three activities produce floral meristems that develop as pseudo flowers; all floral organs are replaced with green leaf like structures in a whorled arrangement. Evolutionary biologists have speculated that floral organs are highly modified leaves. This experiment gives direct support to these ideas.
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1.Each ovule  consists of a  megasporangium,  its protective layer  of surrounding  integuments, and  its stalk 2. Three of the  four meiotic  products  degenerate 3. The embryo sac is  the female  gametophyte and  contains eight  haploid nuclei 4. Micrograph shows  several developing  pollen grains in the  anthers 5. The pollen grain is 
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