Chapter 33 Notes - Control in Plants

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Control in Plants

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Chapter 33 Notes - Control in Plants

  1. 1. Chapter 33 Control Systems in Plants 0
  2. 2. <ul><li>What Are the Health Benefits of Soy? </li></ul><ul><ul><li>Soy protein </li></ul></ul><ul><ul><ul><li>Is one of the few plant proteins that contains all the essential amino acids </li></ul></ul></ul>
  3. 3. <ul><ul><li>Phytoestrogens, a class of plant hormones </li></ul></ul><ul><ul><ul><li>Are found in soy </li></ul></ul></ul>CH 3 OH HO HO O OH OH O Estrogen (Estradiol) Phytoestrogen (Genistein) Chemical structures of a human estrogen and a plant phytoestrogen
  4. 4. <ul><ul><li>Soy products contain isoflavones </li></ul></ul><ul><ul><ul><li>A type of phytoestrogen that may provide human health benefits </li></ul></ul></ul>Soybeans
  5. 5. PLANT HORMONES <ul><li>33.1 Experiments on how plants turn toward light led to the discovery of a plant hormone </li></ul><ul><ul><li>Plants exhibit phototropism </li></ul></ul><ul><ul><ul><li>The growth of shoots in response to light </li></ul></ul></ul>Figure 33.1A
  6. 6. <ul><ul><li>Microscopic observations of plants </li></ul></ul><ul><ul><ul><li>Indicate that a cellular mechanism underlies phototropism </li></ul></ul></ul>Figure 33.1B Shaded side of shoot Illuminated side of shoot Light
  7. 7. <ul><li>Showing That Light Is Detected by the Shoot Tip </li></ul><ul><ul><li>Charles Darwin showed that the tip of a grass seedling detects light </li></ul></ul><ul><ul><ul><li>And transmits a signal down to the growing region of a shoot </li></ul></ul></ul>Figure 33.1C Light Control Tip removed Tip covered by opaque cap Tip covered by trans- parent cap Base covered by opaque shield Tip separated by gelatin block Tip separated by mica Darwin and Darwin (1880) Boysen-Jensen (1913)
  8. 8. <ul><li>Isolating the Chemical Signal </li></ul><ul><ul><li>The hormone auxin </li></ul></ul><ul><ul><ul><li>Was determined to affect phototropism </li></ul></ul></ul><ul><ul><ul><li>Promotes faster cell elongation on the shaded site of the shoot </li></ul></ul></ul>Figure 33.1D Agar Shoot tip placed on agar block. Chemical (later called auxin) diffuses from shoot tip into agar. Other controls: Blocks with no chemical have no effect. Offset blocks with chemical stimulate curved growth. Control Block with chemical stimulates growth. No light
  9. 9. <ul><li>33.2 Five major types of hormones regulate plant growth and development </li></ul><ul><ul><li>Even in small amounts, plant hormones </li></ul></ul><ul><ul><ul><li>Trigger signal transduction pathways </li></ul></ul></ul><ul><ul><ul><li>Regulate plant growth and development </li></ul></ul></ul>
  10. 10. <ul><ul><li>The major types of plant hormones </li></ul></ul>Table 33.2
  11. 11. <ul><li>33.3 Auxin stimulates the elongation of cells in young shoots </li></ul><ul><ul><li>Plants produce auxin (IAA) </li></ul></ul><ul><ul><ul><li>In the apical meristems at the tips of shoots </li></ul></ul></ul>
  12. 12. <ul><ul><li>At different concentrations, auxin </li></ul></ul><ul><ul><ul><li>Stimulates or inhibits the elongation of shoots and roots </li></ul></ul></ul>Figure 33.3A, B Roots Stems 0 0.9 g/L   10 – 8 10 – 6 10 – 4 10 – 2 1 10 2 Increasing auxin concentration (g/L) Elongation Inhibition Promotion
  13. 13. <ul><ul><li>Auxin may act by weakening cell walls </li></ul></ul><ul><ul><ul><li>Allowing them to stretch when cells take up water </li></ul></ul></ul>Plasma membrane Cell wall H + 1 2 H + 3 H 2 O Vacuole Cell elongation Cellulose loosens; cell can elongate Cellulose molecule Cross-linking molecule Enzyme Cellulose molecule Cell wall Cytoplasm H + pump (protein) Figure 33.3C
  14. 14. <ul><ul><li>Auxin promotes growth in stem diameter </li></ul></ul><ul><ul><ul><li>By stimulating the development of vascular tissues and cell division in vascular cambium </li></ul></ul></ul>
  15. 15. <ul><li>33.4 Cytokinins stimulated cell division </li></ul><ul><ul><li>Cytokinins </li></ul></ul><ul><ul><ul><li>Are produced by growing roots, embryos, and fruits </li></ul></ul></ul><ul><ul><ul><li>Promote cell division </li></ul></ul></ul>
  16. 16. <ul><ul><li>Cytokinins from roots may balance the effects of auxin from apical meristems </li></ul></ul><ul><ul><ul><li>Causing lower buds to develop into branches </li></ul></ul></ul>Figure 33.4 Terminal bud No terminal bud
  17. 17. <ul><li>33.5 Gibberellins affect stem elongation and have numerous other effects </li></ul><ul><ul><li>Gibberellins </li></ul></ul><ul><ul><ul><li>Stimulate the elongation of stems </li></ul></ul></ul>Figure 33.5A
  18. 18. <ul><ul><li>Gibberellins </li></ul></ul><ul><ul><ul><li>Stimulate the development of fruit </li></ul></ul></ul><ul><ul><ul><li>Function in embryos in some of the early events of seed germination </li></ul></ul></ul>Figure 33.5B
  19. 19. <ul><li>33.6 Abscisic acid inhibits many plant processes </li></ul><ul><ul><li>Abscisic acid (ABA) </li></ul></ul><ul><ul><ul><li>Inhibits the germination of seeds </li></ul></ul></ul><ul><ul><li>The ratio of ABA to gibberellins </li></ul></ul><ul><ul><ul><li>Often determines whether a seed will remain dormant or germinate </li></ul></ul></ul>
  20. 20. <ul><ul><li>Seeds of many plants remain dormant </li></ul></ul><ul><ul><ul><li>Until their ABA is inactivated or washed away </li></ul></ul></ul>Figure 33.6
  21. 21. <ul><ul><li>ABA also acts as a “stress hormone” </li></ul></ul><ul><ul><ul><li>Causing stomata to close when a plant is dehydrated </li></ul></ul></ul>
  22. 22. <ul><li>33.7 Ethylene triggers fruit ripening and other aging processes </li></ul><ul><ul><li>As fruit cells age </li></ul></ul><ul><ul><ul><li>They give off ethylene, which triggers a variety of aging processes </li></ul></ul></ul>
  23. 23. <ul><li>Fruit Ripening </li></ul><ul><ul><li>Ethylene </li></ul></ul><ul><ul><ul><li>Triggers fruit ripening </li></ul></ul></ul>Figure 33.7A 1 2 3
  24. 24. <ul><li>The Falling of Leaves </li></ul><ul><ul><li>A changing ratio of auxin to ethylene </li></ul></ul><ul><ul><ul><li>Is triggered by shorter days </li></ul></ul></ul><ul><ul><ul><li>Probably causes autumn color changes and the loss of leaves from deciduous trees </li></ul></ul></ul>Figure 33.7B Leaf stalk Stem (twig) Abscission layer Protective layer Stem Leaf stalk LM 20 
  25. 25. CONNECTION <ul><li>33.8 Plant hormones have many agricultural uses </li></ul><ul><ul><li>Farmers use auxin </li></ul></ul><ul><ul><ul><li>To delay or promote fruit drop </li></ul></ul></ul>Figure 33.8
  26. 26. <ul><ul><li>Auxins and gibberellins </li></ul></ul><ul><ul><ul><li>Are used to produce seedless fruits </li></ul></ul></ul><ul><ul><li>A synthetic auxin called 2,4-D </li></ul></ul><ul><ul><ul><li>Is used to kill weeds </li></ul></ul></ul><ul><ul><ul><li>Has safety questions associated with its use </li></ul></ul></ul>

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