Plant Regulation

1. Plant Regulation Chapter 39

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

9. Auxin • First plant hormone • (IAA) Indoleacetic acid • Found in apical meristems of shoots • Promotes activity of vascular cambium • Promotes lateral root growth • Found in pollen, fruit development

10. Auxins • Plasticity (soften) of plant • Elongation of plant • Auxin moves from light exposed side • To shady side • Bends towards light

13. Auxins • Synthetic auxins • Prevent apples from dropping early • Berries on holly • Seedless tomatoes • Control weeds

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

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

16. 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

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

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

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

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

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

22. Ethylene • Mechanical stress on stem tip. • Triple response • Enables a seedling to avoid an obstacle.

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

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

25. 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

26. Light response • Acts as switching mechanism • Controls various light-induced events • Phytochrome exposed to red light • Pr is converted to Pfr • Triggering germination • Far-red light inhibits germination

27. Light response

28. Light response • Determine plant spacing • Pfr plant grows tall • Pr plant branches

29. Circadian clocks

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

31. 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

32. Touch response • Thigmotropism • Directional growth response • Direction of touch • Object, animal, wind • Thigmonastic • Responds in one direction • Despite where the contact is

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

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

35. Turgor movement • Environmental stimuli • Rapid loss of K+ out of half the pulvini cells • Water follows • Causes cells to be flaccid • Leaves fold in • Reverses in approx 15-30 minutes

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37. Dormancy • Survive environment extremes • Signals that initiate or terminate dormancy • Temperate regions dormancy occurs during winter (day-length) • Dry climates dormancy comes in summer (rainfall)

38. Plant defense • First defense • Dermal tissue system • Cutin, suberin • Bark, thorns, trichomes

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

40. Plant defense • Soy products produce Phytoestrogens • Similar in structure to estrogen • Decreased prostate cancer in Asian men • Help minimize menopausal symptoms

41. Plant defense • Pacific Yew produces Taxol • Fights cancer especially breast cancer • Cinchona tree bark Quinine • Anti-malaria drug

42. Plant defenses • Toxic when metabolized by herbivore

43. Plant defense • Allelopathy: • When a chemical secreted by roots • Inhibits growth of other plants • Black walnut trees

44. Plant defense • 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

45. Wasps