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Control Systems in Plants

Control Systems in Plants. Plant Hormones. Coordinates growth Coordinates development Coordinates responses to environmental stimuli. Plant Hormones. Auxin (IAA) Cytokinins Gibberllins Abscisic Acid Ethylene Oligogaccharins Brassinosteroids. Auxins. Stimulates stem elongation

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Control Systems in Plants

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  1. Control Systems in Plants

  2. Plant Hormones • Coordinates growth • Coordinates development • Coordinates responses to environmental stimuli

  3. Plant Hormones • Auxin (IAA) • Cytokinins • Gibberllins • Abscisic Acid • Ethylene • Oligogaccharins • Brassinosteroids

  4. Auxins • Stimulates stem elongation • Stimulates root growth • Stimulates differentiation and branching • Stimulates development of fruit • Stimulates apical dominance • Stimulates phototropism and gravitropism

  5. Auxin Control • Auxin stimulates growth • Auxin block on right causes cells to elongate and the plant bends left • Auxin block on left causes cells to elongate the the plant bends right

  6. Polar Transport • Auxin is transported from apex to shoot • Cell wall is acidic • auxin ion picks up H+ • diffuses across plasma membrane • Cytosol is neutral • auxon loses H+ • uses energy to pump out H+ to maintain pH • leaves cell through carrier proteins

  7. Acid Growth Hypothesis • Proton pump stimulated by auxin which lower pH of wall • Hydrogen Ion activates Enzyme • Enzyme breaks hydrogen bonds in cellulose • Wall takes up water and elongates

  8. Auxin Others • Promotes secondary growth by encouraging vascular cambium and secondary xylem • Promotes adventitious root at the base of a cut stem • Promotes fruit growth without pollination (seedless tomatoes)

  9. Cytokinins • Stimulates root growth • Stimulates cell division and differentiation (with auxins) • more cytokinin - shoot buds develop • more auxin - roots develop • Stimulates germination • Delays Senescence

  10. Gibberellins • Promotes seed and bud germination • Promotes stem elongation • Promotes leaf growth • Stimulates flowering and fruits • (with auxin)

  11. Abscisic Acid • Inhibits growth (with gibberellins) • Closes stomata under water stress • Permits dormancy

  12. Ethylene • Promotes fruit ripening • Controls Abscission • (with auxin)

  13. Oligosaccharins • Triggers defense responses against pathogens • Regulates growth

  14. Brassinosteroids • Required for normal growth and development

  15. Signal-Transduction Pathways • A hormone binds to receptor and stimulates secondary messengers which Activates cell responses

  16. Plant Movements • Phototropism • Gravitropism • Thigmotropism

  17. Plant Movement • Rapid Leaf Movement • drop in turgor pressure within pulvini (at joints of the leaf) • sent by action potentials • Sleep Movements • cells on opposite sides of pulvinus control the movement

  18. Daily and Seasonal Responses • Circadian Rhythm • Photoperiodism • controls flowering (short-day vs. long-day) • critical night length

  19. Photoperiodic Control

  20. Flowering Hormones • Experiment indicates the presence of some type of flowering hormone

  21. Phytochromes • Function as photoreceptors / red (660nm) to far red (730nm) • Activates kinases (regulatory proteins)

  22. Red vs. Far Red Response

  23. Plant Responses to Environmental Stress • Water Deficit • Oxygen Deprivation • Salt Stress • Heat Stress • Cold Stress • Herbivores

  24. Water Deficit • Slows Transpiration • stomata close • release of abscisic acid • Inhibits growth of young leaves • Change leaf shape • Deeper root growth

  25. Oxygen Deprivation • Aerial roots • Production of air tubes

  26. Salt Stress • Salt glands • Compatible solutes

  27. Heat Stress • Heat-shock proteins

  28. Cold Stress • Altering the lipid composition of their membranes • Changes in the solute composition of the cytosol

  29. Responses to Herbivores • Produce Canavanine • Recruitment of predatory animals

  30. Defense Against Pathogens • Gene-for-gene recognition

  31. Defense Against Pathogens • Hypersensitive response (HR) • phytoalexins are released • PR proteins are released • Seal off infected area • Systemic acquired resistance (SAR) • Salicylic acid released due to death of cell • Activates a Signal Transduction Pathway • Activates SAR

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