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Plant hormones and growth regulators

Plant hormones and growth regulators. Hormones Auxins Cytokinins Gibberellins (GA) Ethylene (ethene) Abscisic acid (ABA). Other growth regulators Brassinosteroids Salicylic acid (SA) Jasmonic acid (JA) Systemin. Plant Hormone: Auxin. Auxin role:

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Plant hormones and growth regulators

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  1. Plant hormones and growth regulators • Hormones • Auxins • Cytokinins • Gibberellins (GA) • Ethylene (ethene) • Abscisic acid (ABA) • Other growth regulators • Brassinosteroids • Salicylic acid (SA) • Jasmonic acid (JA) • Systemin

  2. Plant Hormone: Auxin Auxin role: http://www.youtube.com/watch?v=zctM_TWg5Ik ALL Pea Mustard and Corn

  3. Auxin regulates apical dominance Apical dominance = the growing apical bud inhibits the growth of lateral (axillary) buds Phaseolus vulgaris (bean) Removal of apical/ terminal bud induces growth of axillary buds Applying IAA to cut surface prevents outgrowth of axillary buds Axillary buds are suppressed because of apical dominance

  4. Auxin: induces shoot elongation

  5. Auxin: Multiple Biosynthetic Pathways IAN: Indole -3-acetonitrile Pathway TAM: Tryptamine Pathway IAM: Indole-3-acidamide Pathway IPA: Indole-3-pyruvate pathway

  6. Polar Auxin Transport

  7. Auxin: Signal Transduction Pathway

  8. Dark side of Auxins • The compound 2,4-D is still in use and is thought to be safe • 2,4,5-T banned by the EPA in 1979. • The Dioxin is an unavoidable contaminant produced in the manufacture of 2,4,5-T. Implicated in leukemia, miscarriages, birth defects, liver damage, and other diseases. • Agent Orange was sprayed in Vietnam as a defoliant to deny ground cover to the Vietnamese army. The defoliant Agent Orange was a mix of 2,4-D and 2,4,5-T. http://en.wikipedia.org/wiki/Auxin

  9. Growth Hormone: AuxinThings to Remember • Plant hormones and growth regulators • Name the plant hormones and growth regulators • Role of auxin in plant development • Gravitropism, phototropism • Roles in Agronomy • IAA-myo-inositol hydrolyzed in endosperm and transported to germinating coleoptile in free form • Polar auxin transport requires energy, independent of gravity • Tryptophan is the precursor for biosynthesis of Auxin • Consistent with Tryptophan synthesis in plastids, 1/3 of total IAA is found in plastids. • Parthenocarpy • Auxin signal transduction pathway regulates expression of Auxin responsive genes. • Genes AUX1 (auxin influx transport) and PIN1 (Auxin efflux transport)

  10. The tryptophan- dependent pathway Evidence: • Isotope feeding • Mutant analysis: the yucca mutant, but no auxin deficient mutant Yucca 10

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