Plant Growth & Development 3 stages Embryogenesis Fertilization to seed 2. Vegetative growth

1. Plant Growth & Development 3 stages • Embryogenesis Fertilization to seed 2. Vegetative growth Juvenile stage Germination to adult "phase change" marks transition 3. Reproductive development Make flowers, can reproduce sexually

2. Basic pattern offloral development A, B, C genes = transcription factors http://en.wikipedia.org/wiki/File:Flower_poster_2.jpg

3. The ABC model: model forfloral organ identity determination • Homeotic transformations • formation of a normal plant/animal body structure in place of another at an abnormal site • e.g., sepals forming in the 2nd whorl • ABC model: E. Coen and E. Meyerowitz 1991 Arabidopsis Antirrhinum http://biology.kenyon.edu/courses/biol114/Chap13/Chapter_12C.html

4. The ABC model: model forfloral organ identity determination Sepal formation: needs class A genes Petal: A + B Stamen: B + C Carpel: C • Mutual inhibition of class A and class C function http://www.its.caltech.edu/~plantlab/html/research.html

5. Sexual reproduction • haploid gametogenesis in flowers: reproductive organs • Female part = pistil (gynoecium) • Stigma • Style • Ovary • Ovules • Male part : • anthers • Make pollen

6. Sexual reproduction 1. making haploid gametes in flowers • Pollen = male, 2-3 cells • Made in anther locules Archesporial cell Primarysporogenouscells Primaryparietalcells (Wilson & Yang, 2004, Reproduction) 2o parietal cells Pollen mothercells Endothecium meiosis Middle cell layer Tapetum Microspores

7. Sexual reproduction 1. making haploid gametes in flowers • Pollen = male, contains 2-3 cells • Made in anthers • Microspores divide to form vegetative cell and germ cell • Germ cell divides to form 2 sperm cells, but often not until it germinates • Pollen grains dehydrate and are coated • Are released, reach stigma, then germinate

8. Sexual reproduction 1. making haploid gametes in flowers • Pollen = male, contains 2-3 cells • Egg = female, made in ovaries

9. Sexual reproduction • Megaspore mother cell → meiosis → 4 haploid megaspores • 3 die • Functional megaspore divides 3 x w/o cytokinesis • Cellularization forms egg, binucleate central cell, 2 synergids & 3 antipodals http://www.biologie.uni-hamburg.de/b-online/library/webb/BOT201/Angiosperm/MagnoliophytaLab99/OvuleForm700.jpg

10. Sexual reproduction Pollen lands on stigma & germinates if good signals • Forms pollen tube that grows through style to ovule • Germ cell divides to form sperm • nuclei Pollen tube reaches micropyle & releases sperm nuclei into ovule

11. Sexual reproduction Pollen tube reaches micropyle & releases sperm nuclei into ovule Double fertilization occurs! One sperm fuses with egg to form zygote Other fuses with central cell to form 3n endosperm

12. Embryogenesis One sperm fuses with egg to form zygote Other fuses with central cell to form 3n endosperm Development starts immediately!

13. Embryogenesis Development starts immediately! Controlled by genes, auxin & cytokinins Apical cell after first division becomes embryo, basal cell becomes suspensor

14. Embryogenesis Development starts immediately! Controlled by genes, auxin & cytokinins Apical cell after first division becomes embryo, basal cell becomes suspensor Key events Establishing polarity: starts @ 1st division

15. Embryogenesis Establishing polarity: starts @ 1st division Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue

16. Embryogenesis Establishing polarity: starts @ 1st division Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue Forming the root and shoot meristems

17. Embryogenesis Establishing polarity: starts @ 1st division Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue Forming the root and shoot meristems Forming cotyledons & roots

18. Embryogenesis Establishing polarity: starts @ 1st division Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue Forming the root and shoot meristems Forming cotyledons & roots Body plan is formed during embryogenesis: seedling that germinates is a juvenile plant with root and apical meristems

19. Embryogenesis End result is seed with embryo packaged inside protective coat

20. Embryogenesis End result is seed with embryo packaged inside protective coat Endosperm feeds developing embryo (3n grows faster)

21. Embryogenesis End result is seed with embryo packaged inside protective coat Endosperm feeds developing embryo (3n grows faster) In many dicots endosperm is absorbed as seed develops

22. Embryogenesis End result is seed with embryo packaged inside protective coat Endosperm feeds developing embryo (3n grows faster) In many dicots endosperm is absorbed as seed develops In many monocots endosperm is seedling food

23. Embryogenesis Body plan is formed during embryogenesis: seedling that germinates is a juvenile plant with root and apical meristems, roots & shoots

24. Embryogenesis Body plan is formed during embryogenesis: seedling that germinates is a juvenile plant with root and apical meristems, roots & shoots Later stages of seed development load nutrients and form protective coat

25. Embryogenesis Later stages of seed development load nutrients and form protective coat Final stages involve desiccation (to 5% moisture content) & dormancy

26. Embryogenesis Later stages of seed development involve loading nutrients and forming protective coat Final stages involve desiccation (to 5% moisture content) & dormancy -> Abscisic acid plays important role

27. Embryogenesis Later stages of seed development load nutrients and form protective coat Final stages involve desiccation (to 5% moisture content) & dormancy -> Abscisic acid plays important role Coordinated with fruit ripening: fruit’s job is to protect & disperse seed

28. Seed germination Coordinated with fruit ripening: fruit’s job is to protect & disperse seed Seeds remain dormant until sense appropriate conditions: some date palms germinated after 2000 years!

29. Seed germination • Seeds remain dormant until sense appropriate conditions: • some date palms germinated after 2000 years! • Water

30. Seed germination • Seeds remain dormant until sense appropriate conditions: • some Lotus germinated after 2000 years! • Water • Temperature: some seeds require vernalization = prolonged cold spell

31. Seed germination • Seeds remain dormant until sense appropriate conditions: • some Lotus germinated after 2000 years! • Water • Temperature: some seeds require vernalization = prolonged cold spell • May degrade hydrophobic seed coat

32. Seed germination • Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • May degrade hydrophobic seed coat • May disperse inhibitor (eg Abscisic acid)

33. Seed germination • Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • May degrade hydrophobic seed coat • May disperse inhibitor (eg Abscisic acid) • Many require light

34. Seed germination • Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • May degrade hydrophobic seed coat • May disperse inhibitor (eg Abscisic acid) • Many require light: says that they will soon be able to photosynthesize

35. Seed germination • Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • May degrade hydrophobic seed coat • May disperse inhibitor (eg Abscisic acid) • Many require light: says that they will soon be able to photosynthesize: often small seeds with few reserves

36. Seed germination • Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • Many require light: says that they will soon be able to photosynthesize: often small seeds with few reserves • Some need acid treatment or scarification

37. Seed germination • Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • Many require light: says that they will soon be able to photosynthesize: often small seeds with few reserves • Some need acid treatment or scarification • Passage through bird gut

38. Seed germination • Seeds remain dormant until sense appropriate conditions: • Water • Temperature • Many require light • Some need acid treatment or scarification • Passage through bird gut • Some need fire

39. Seed germination • Seeds remain dormant until sense appropriate conditions: • Some need acid treatment or scarification • Passage through bird gut • Some need fire • Hormones can also trigger (or stop) germination

40. Seed germination • Seeds remain dormant until sense appropriate conditions: • Hormones can also trigger (or stop) germination • Germination is a two step process • Imbibition is purely physical: seed swells as it absorbs water until testa pops. Even dead seeds do it.

41. Seed germination • Germination is a two step process • Imbibition is purely physical: seed swells as it absorbs water until testa pops. Even dead seeds do it. • Next embryo must start metabolism and cell elongation

42. Seed germination • Germination is a two step process • Imbibition is purely physical: seed swells as it absorbs water until testa pops. Even dead seeds do it. • Next embryo must start metabolism and cell elongation • This part is sensitive to the environment, esp T & pO2

43. Seed germination • Germination is a two step process • Imbibition is purely physical: seed swells as it absorbs water until testa pops. Even dead seeds do it. • Next embryo must start metabolism and cell elongation • This part is sensitive to the environment, esp T & pO2 • Once radicle has emerged, vegetative growth begins

44. Vegetative growth • Once radicle has emerged, vegetative growth begins • Juvenile plants in light undergo photomorphogenesis • Initially live off reserves, but start • making photosynthetic leaves

45. Vegetative growth • Once radicle has emerged, vegetative growth begins • Juvenile plants in light undergo photomorphogenesis • Initially live off reserves, but start • making photosynthetic leaves • Roots grow down seeking • water & nutrients

46. reproductive phase • Eventually switch to reproductive phase & start flowering • Are now adults!

47. reproductive phase • Eventually switch to reproductive phase & start flowering • Are now adults! • Time needed varies from days to years

48. reproductive phase • Eventually switch to reproductive phase & start flowering • Are now adults! • Time needed varies from days to years. • Shoot apical meristem now starts making new organ: flowers, with many new structures & cell types

49. Plan B schedule- Spring 2013 • Date TOPIC • JAN 14 General Introduction • 16 plant structure I • 18 plant structure II • 21 plants and water I • 23 plants and water II • 25 mineral nutrition I • 28 mineral nutrition II • 30 solute transport I • FEB 1 solute transport II • 4 Photosynthetic light reactions I • 6 Photosynthetic light reactions II • 8 Calvin cycle • 11 C4 and CAM • 13 Environmental effects • 15 Phloem transport I • 18 Exam 1

50. 20 Phloem transport II 22 Respiration I 25 Respiration II 27 Respiration III MAR 1 Lipid synthesis 4 Spring Recess 6 Spring Recess 8Spring Recess 11 Biofuels 13 Nutrient assimilation I 15 Nutrient assimilation II 18 Cell wall synthesis and growth I 20 Cell wall synthesis and growth II 22 Growth and development I 25 Growth and development II 27 Light regulation of growth I 29Easter APR 1Easter