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Plant Regulation

Plant Regulation. Chapter 39. Plant growth. Plants respond to environment Growth response to abiotic factors Water, wind and light. Plant responses. Light Gravity Touch Water Temperature. Plant hormones. Internal signal (developmental) Environmental signal Chemical binds receptor

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Plant Regulation

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  1. Plant Regulation Chapter 39

  2. Plant growth • Plants respond to environment • Growth response to abiotic factors • Water, wind and light

  3. Plant responses • Light • Gravity • Touch • Water • Temperature

  4. Plant hormones • Internal signal (developmental) • Environmental signal • Chemical binds receptor • Physiological response • Developmental response • Reception-transduction-response • Regulate growth & development • New protein or activation of protein

  5. Light response • Photomorphogenesis: • Nondirectional light-triggered development • Change in form • Flower formation • Phototropisms: • Directional development • Trope (turn)

  6. Plant hormones • Auxin • Cytokinins • Gibberellins • Brassinosteriods • Ethylene • Abscisic acid

  7. Auxin • First plant hormone • (IAA) Indoleacetic acid • Found in apical meristems of shoots • Plasticity (soften) of plant • Elongation of plant

  8. Auxins • Auxin moves from light exposed side • To the shady side • Promotes growth & elongation • Helps plants response to environment • Promotes activity of vascular cambium • Promotes lateral root growth • Found in pollen, fruit development

  9. Auxins • Synthetic auxins • Prevent apples from dropping early • Berries on holly • Seedless tomatoes (green house tomatoes) • Control weeds (higher dose, prevents axial growth)

  10. Cytokinins • Purines • Similar structure to adenine • Cell division & differentiation • Found in root apical meristems • Transported through plant • Lateral buds into branches • Inhibit lateral roots (auxin promotes)

  11. Cytokinins • Remove terminal bud • Plant becomes bushier • Promotes lateral buds into branches • Auxin on cut surface • Inhibits lateral buds

  12. Cytokinins • Applied to cut leaves prevent aging • Florists spray on fresh cut flowers • Crown gall • Tumor growth on trees • Bacteria causes increased production of auxin & cytokinins

  13. Gibberellins • Stem elongation • Enhances if auxin present • Found in apical portions of stems & roots • Apply to dwarf plants restores normal growth

  14. Gibberellins • Stimulate enzymes that utilize food during germination • Hastens germination • Fruit development • Helps space grape leaves (internodes) • Fruits have more space to grow

  15. Brassinosteriods • Similar in structure to testosterone, estradiol, cortisol • Elongation & cell division • Bending of stems • Reproductive development • Delays senescence

  16. Abscisic Acid • Found in mature green leaves, fruit & root caps • Formation of winter buds • Induce seed dormancy • Controls stomata open/close

  17. Ethylene • Gas • Suppresses stem & root elongation • Hastens fruit ripening • Response to stress • Leaf abscission • Programmed cell death

  18. Ethylene • Mechanical stress on stem tip. • Triple response • Enables a seedling to avoid an obstacle. • Stem elongation slows, • Stem thickens, • Curvature causes the stem to start growing horizontally.

  19. Ethylene • Commercially sprayed on green tomatoes • Hastens ripening

  20. Light response • Certain wavelengths of light • Initiate biological change • Phytochrome: • Pigment containing protein • Two forms Pr (inactive form) and Pfr(active form)

  21. Light response • Inter-convertible forms • Pr absorbs red light (660nm) • Converts to the active form Pfr • Pfr absorbs far red light (730 nm) • Converts to the inactive form Pr

  22. Light response • Inter-conversion acts as switching mechanism • Controls various light-induced events • Pfr form triggers plant’s developmental responses to light. • Exposure to far-red light inhibits the germination response.

  23. Light response

  24. Light response • Seeds exposed to sunlight • Phytochrome exposed to red light • Pr is converted to Pfr • Triggering germination.

  25. Light response • Determine spacing between plants • Pfr plant grows tall • Pr plant branches

  26. Circadian clocks

  27. Gravity response • Gravitropism • Response of plant to gravitational pull • Shoot negative gravitropic response • Roots positive gravitropic response

  28. Gravity response • Response present at germination • Stem • Greater concentration of a elongation hormone on the under side • Cells grow more then upper side • Root • Upper cells grow more rapidly • Root grows down

  29. Gravity response • Amyloplasts: • Starch containing organelles • Maybe involved in sensing gravity • Stem located in the endoplasm • Root located in the root cap • Root cap is involved in sensing gravity

  30. Touch response • Thigmotropism • Directional growth response • In direction of touch • Object, animal, wind • Thigmonastic • Responds in one direction despite where the contact is

  31. Touch response • Tendril touches an object • Uneven growth • Wraps around the object • Fly trap • Touch hairs, closes (0.3 sec)

  32. media\39_26MimosaLeaf_SV.mpg

  33. Turgor Movement • Touch induces change in turgor • Cells collapse • Causes leaf movement • Pulvini: • Multicellular swellings at the base of the leaf or leaflet

  34. Turgor movement • Stimuli such as wind, touch, heat • Rapid loss of K+ out of half the pulvini cells • Water follows • Causes cells to be flaccid • Leaves fold in • Mimosa • Reverses in approx 15-30 minutes

  35. Dormancy • Survive environment extremes • Plant have a dormant stage • Temperature, light & water • Signals that initiate or terminate dormancy • Temperate regions dormancy occurs during winter (day-length) • Dry climates dormancy comes in summer (rainfall)

  36. Plant defense • First defense • Dermal tissue system • Cutin, suberin • Bark, thorns, trichomes • Nematodes, fungi, bugs still penetrate these defenses

  37. Plant defense • Poisons • Cyanide-containing compounds • Stops electron-transport • Cassava (African food) • Secondary metabolites • Alkaloids (caffeine, nicotine, cocaine, and morphine)

  38. Secondary metabolites • Soy products produce Phytoestrogens • Similar in structure to human estrogen • Decreased prostate cancer in Asian men • Help minimize menopausal symptoms

  39. Secondary metabolites • Pacific Yew produces Taxol • Helps fight cancer especially breast cancer • Cinchona tree bark Quinine • Anti-malaria drug • Designed to harm herbivores

  40. Plant defenses • 1. Toxin in membrane-bound structure • 2. Poison toxic when metabolized by herbivore

  41. Allelopathy • Chemical secreted by roots of one plant • Inhibits growth of other plants • Black walnut trees

  42. Plant response • Plant is injured • Cell death at location • Prevents further spread of pathogen • H2O2 & NO can be produced • Can cause harm to invader • Chemicals released to warn other plants of an invasion

  43. Wasps

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