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Chapter 38

Chapter 38. Angiosperm Reproduction. Angiosperms have 3 unique F eatures:. F lowers F ruits Double F ertilization (by 2 sperm). REPRODUCTIVE VARIATIONS. https://www.sciencelearn.org.nz/resources/77-pollination-and-fertilisation. Pollination : transfer pollen from anther to stigma.

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Chapter 38

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  1. Chapter 38 Angiosperm Reproduction

  2. Angiosperms have 3 unique Features: • Flowers • Fruits • Double Fertilization (by 2 sperm)

  3. REPRODUCTIVE VARIATIONS https://www.sciencelearn.org.nz/resources/77-pollination-and-fertilisation

  4. Pollination: transfer pollen from anther to stigma

  5. Stigma Stigma • Some plants are self-pollinated • Cross-pollinated plants: • Self-incompatibility: plant rejects own pollen or closely related plant • Maximize genetic variation Anther with pollen Pin flower Thrum flower “Pin” and “thrum” flower types reduce self-fertilization

  6. The development of a plant embryo https://www.youtube.com/watch?v=X7zW5W6XGeg

  7. Fruit • Egg cell  plant embryo • Ovulesinside ovary  seeds • Ripe ovary fruit • Fruit protects enclosed seed(s) • Aids in dispersal by water, wind, or animals

  8. Seeds Mature seed  dormancy (resting) • Low metabolic rate • Growth & development suspended • Resumes growth when environmental conditions suitable for germination

  9. Germination • Seed take up water (imbibition)  trigger metabolic changes to begin growth • Root develops  shoot emerges  leaves expand & turn green (photosynthesis) • Very hazardous for plants due to vulnerability • Predators, parasites, wind

  10. Plant Reproduction

  11. Asexual reproduction in aspen trees Test-tube cloning of carrots

  12. Humans Modify Crops • Artificial selection of plants for breeding • Plant Biotechnology: • Genetically modified organisms • “Golden Rice”: engineered to produce beta-carotene (Vit. A) • Bt corn: transgenic – expresses Bt (bacteria) gene  produces protein toxic to insects • Biofuels – reduce CO2 emissions • Biodiesel: vegetable oils • Bioethanol: convert cellulose into ethanol

  13. Practice Questions!

  14. Chapter 39 Plant Responses to Internal and External Signals

  15. POGIL: Plant Hormones ____________________________________ turn in the POGIL for your group with sticky note on top.

  16. POGIL: Plant Hormones Person with the highest 3Q grade (so far) turns in the POGIL for your group with sticky note on top.

  17. Experiments with Light and the coleoptile

  18. Cells on darker side elongate faster than cells on brighter sideAUXIN = chemical messenger that stimulates cell elongation Excised tip placed on agar block Growth-promoting chemical diffuses into agar block Control (agar block lacking chemical) has no effect Agar block with chemical stimulates growth Offset blocks cause curvature Control

  19. Important plant hormones: • Auxin – stimulate cell elongation  phototropism & gravitropism (high concentrations = herbicide) • Cytokinins – cell division (cytokinesis) & differentiation • Gibberellins – stem elongation, leaf growth, germination, flowering, fruit development • Abscisic Acid – slows growth; closes stomata during H2O stress; promote dormancy • Ethylene – promote fruit ripening (positive feedback!); involved in apoptosis (shed leaves, death of annuals)

  20. The effects of gibberellin on stem elongation and fruit growth

  21. Ethylene Gas: Fruit Ripening Canister of ethylene gas to ripen bananas in shipping container Untreated tomatoes vs. Ethylene treatment

  22. Plant Movement • Tropisms: growth responses  SLOW • Phototropism – light (auxin) • Gravitropism – gravity (auxin) • Thigmotropism – touch • Turgor movement: allow plant to make relatively rapid & reversible responses • Venus fly trap, mimosa leaves, “sleep” movement

  23. Positive gravitropism in roots: the statolith hypothesis.

  24. Thigmotropism: rapid turgor movements by Mimosa plant  action potentials

  25. Plant Responses to Light • Plants can detect direction, intensity, & wavelenth of light • Phytochromes: light receptors, absorbs mostly red light • Regulate seed germination, shade avoidance

  26. Biological Clocks Circadian rhythm: biological clocks • Persist w/o environmental cues • Frequency = 24 hours Phytochrome system + Biological clock = plant can determine time of year based on amount of light/darkness

  27. Photoperiodism: physiological response to the relative length of night & day (i.e. flowering) • Short-day plants: flower when nights are long (mums, poinsettia) • Long-day plant: flower when nights are short (spinach, iris, veggies) • Day-neutral plant: unaffected by photoperiod (tomatoes, rice, dandelions)

  28. Practice Questions!

  29. Plant responses to stress

  30. Drought (H2O deficit): • close stoma • release abscisic acid to keep stoma closed • Inhibit growth • roll leaves  reduce SA & transpiration • deeper roots • Flooding (O2 deprivation): • release ethylene  root cell death  air tubes formed to provide O2 to submerged roots

  31. Excess Salt: • cell membrane – impede salt uptake • produce solutes to ↓ψ - retain H2O • Heat: • evap. cooling via transpiration • heat shock proteins – prevent denaturation • Cold: • alter lipid composition of membrane (↑unsat. fatty acids, ↑fluidity) • increase cytoplasmic solutes • antifreeze proteins

  32. Herbivores: • physical (thorns) • chemicals (garlic, mint) • recruit predatory animals (parasitoid wasps) • Pathogens: • 1st line of defense = epidermis • 2nd line = pathogen recognition, host-specific

  33. Bozeman Science: Plant Control • https://www.youtube.com/watch?v=HdwIcIkSoBY&feature=youtu.be

  34. Practice • Complete the plant packet. • Show me for credit. • Check answers on bulletin board

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