1. Angiosperm Development

2. Embryogenesis Establishes body plan of the plant Establishes body plan of the plant  Apical-based pattern  Radial pattern Accompanies seed development Accompanies seed development 2

3. Formation of the Embryo Early stages same in all angiosperms Early stages same in all angiosperms  Terminal cell == apical cell  Basal cell anchors embryo at micropyle Polarity! Polarity! Divisions  embryo proper + suspensor Divisions  embryo proper + suspensor 3

4. Primary Meristems Protoderm Protoderm  Periclinal divisions (parallel to surface) Procambiun Procambiun Ground meristem Ground meristem 4

5. Developmental Stages Globular stage (e-h) – precedes cotyledon development Globular stage (e-h) – precedes cotyledon development Globular Stage  Heart Stage (i) Globular Stage  Heart Stage (i)  Monocots – cylindrical Torpedo Stage (k-l) Torpedo Stage (k-l) Development becomes Development becomes restricted to meristems 5

7. Suspensor Supports development of embryo proper Supports development of embryo proper Angiosperm suspensors metabolically active Angiosperm suspensors metabolically active  Fern and gymnosperm suspensors – push embryo into nutritive tissues  Angiosperm suspensor – provides embryo with nutrients and hormones Short-lived Short-lived  Gone by torpedo stage 7

8. Arabidopsis mutants Source of mutations that explain plant development Source of mutations that explain plant development  Expose seed to mutagen  Mutants produce seed 8

9. B – no apical meristem/cotyledons C – no hypocotyl D – no root E – no apical and no basal portions Arabidopsis mutants

10. Which Genes Set Up Body Axes? MONOPTEROS -- sets up apical-basal axis. MONOPTEROS -- sets up apical-basal axis.  Codes for MONOPTEROS protein -- transcription factor.

11. Auxin and Monopteros Auxin – hormone produced in meristem Auxin – hormone produced in meristem Concentration gradient provides positional information Concentration gradient provides positional information Auxin triggers production of regulatory transcription factors Auxin triggers production of regulatory transcription factors  specific to cells in the hypocotyl & roots  Establishes positional axis

12. Mature Embryo & Seed Embryo continually nourished during development Embryo continually nourished during development  Perisperm (from nucellar tissue) within endosperm  Cotyledons Funiculus detaches from ovule  nutritionally closed system Funiculus detaches from ovule  nutritionally closed system Seed dessicates Seed dessicates Seed coat hardens Seed coat hardens 12

13. Mature Embryo Axis bearing cotyledons Axis bearing cotyledons Opposite ends Opposite ends  Shoot apical meristem  Root apical meristem Epicotyl – stemlike axis Epicotyl – stemlike axis  Plumule – embryonic shoot & leaves Hypocotyl – stemlike axis Hypocotyl – stemlike axis  Radicle 13

14. 14

15. Endosperm & Perisperm Some seeds (e.g., beet) contain both Some seeds (e.g., beet) contain both Endosperm – double fertilization Endosperm – double fertilization Perisperm – proliferation of nucellus Perisperm – proliferation of nucellus When endosperm absorbed – large cotyledons When endosperm absorbed – large cotyledons  Sunflower, walnut, pea, bean Large amounts of endosperm – membranous cotyledons Large amounts of endosperm – membranous cotyledons 15

16. Dicot Seeds When endosperm absorbed – large cotyledons When endosperm absorbed – large cotyledons  Sunflower, walnut, pea, bean Large amounts of endosperm – membranous cotyledons Large amounts of endosperm – membranous cotyledons 16

17. Monocot Seeds Grasses – massive cotyledon  scutellum Grasses – massive cotyledon  scutellum  Both radicle & plumule sheathed  Coleorhiza and coleoptile 17

18. Seed Germination Embryo growth delayed while seed matures Embryo growth delayed while seed matures Germination – resumption of embryo growth Germination – resumption of embryo growth  Many factors o External – water, oxygen and temperature Mature seeds typically dry Mature seeds typically dry  Imbibation for enzymatic activity Cells that produced reserve materials now digest Cells that produced reserve materials now digest Cell enlargement & cell division Cell enlargement & cell division Early germination anaerobic Early germination anaerobic  Once seed coat ruptured – process is aerobic! 18

19. Seed Dormancy Physiologically immature embryo Physiologically immature embryo After-ripening After-ripening  Cold periods  Digestion  Fire  Water 19

20. Embryo to Adult First emergent structure – root First emergent structure – root  Anchors plant  Absorbs water Primary root Primary root  Branch or lateral roots Adventitious roots Adventitious roots  Shoot-borne roots 20

21. Epigeal & Hypogeal Germination Epigeal Epigeal  Hypocotyl elongates  hook  Hook straightens  pulls cotyledons & plumule Hypogeal Hypogeal  Epicotyl elongates  hook  Hook straightens  pulls plumule 21

22. Endosperm Present Endosperm Absorbed into Cotyledons Before Germination Epigeous: Cotyledons Emergent Hypogeous: Cotyledons Not Emergent 1. Corn (Monocot) 3. Bean (Dicot) 2. Pea (Dicot) 4. Onion (Monocot) Castor Bean (Dicot) Germination Start Seed Development

23. Type 1 Hypogeous Hypogeous Monocot Monocot Highly differentiated embryo Highly differentiated embryo Endosperm absorbed during germination Endosperm absorbed during germination

24. Type 2 Hypogeous Hypogeous Dicot Dicot Endosperm absorbed well before germination Endosperm absorbed well before germination Cotyledons fill seed Cotyledons fill seed

25. Type 3 Epigeous Epigeous Dicot Dicot Endosperm absorbed well before germination Endosperm absorbed well before germination Cotyledons fill seed Cotyledons fill seed

26. Type 4 Epigeous Epigeous Monocot Monocot Endosperm absorbed during germination Endosperm absorbed during germination

27. Type 4 Epigeous Epigeous Dicot Dicot Endosperm absorbed during germination Endosperm absorbed during germination