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Control Systems in Plants

Control Systems in Plants. Fred Searcy Broward Community College. Hormones. Chemical messengers produced in one location which exert their effect in another location auxins cytokinins ethylene abscissic acid gibberellins. Auxins.

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Control Systems in Plants

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  1. Control Systems in Plants Fred Searcy Broward Community College

  2. Hormones • Chemical messengers produced in one location which exert their effect in another location • auxins • cytokinins • ethylene • abscissic acid • gibberellins

  3. Auxins • Original experiments conducted by Charles and Francis Darwin • published in The Power of Movement in Plants, 1881

  4. Frits W. WentDutch Physiologist (1926)

  5. Auxins • Indoleacetic acid (IAA) - naturally ocurring • 2-4-dichlorophenoxyacetic acid (2-4-D) - synthetic • a-napthalenacetic acid (NAA) - synthetic)

  6. Physiological Effects and Roles of Auxin • Apical dominance • geotropism • phototropism • vascular differentiation • inhibitor of abscission • stimulator of ethylene production • inhibitor and promoter of flowering • stimulates parthenocarpy of fruits • stimulator of adventitious roots

  7. Cytokinins • Skoog & colleagues at University of Wisconsin • use of herring sperm DNA (degredation product stimulated cell division • zeatin (natural) • 6-benzylamino purine (synthetic) • 6N-isopentyladenine (natural)

  8. Cytokinins • Involved with nucleic acids • probably affects gene expression • cell division • organ formation in tissue cultures • leaf senescence • found in roots and shoot tips

  9. Ethylene • 1800’s street lamps caused trees to lose their leaves • fruit maturation • fruit and leaf abscission • plant senescence • sex expression (Cucurbita) females produce more ethylene than males

  10. Abscissic Acid • Dormins (inhibitors) • collected most often from ovaries • abundant for fruit drop • affects root response to gravity • converts vegetative buds to winter buds • antagonistic to auxins

  11. Gibberellins • 1926 Kurosawa (Japan) - foolish seedling disease of rice • caused by the fungus Gibberella fujikuroi • causes stem elongation by stimulating cell division and cell elongation

  12. Gibberellins • Dwarf mutants become normal after treatment • affect cold or light dormancy of seeds • promotes juvenile forms • bolting of rosettes • stimulates pollen germination • stimulates parthenocarpy & larger fruit

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