Plant Responses to Stimuli

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  1. etiolation
    morphological adaptations for growing in darkness
  2. De-etiolation
    after exposure to light, when shoots and roots grow normally
  3. Reception
    internal and external signals are detected by receptors, proteins that change in response to specific stimuli
  4. Transduction
    second messengers transfer and amplify signals from receptors to proteins that cause responses
  5. Response
    • -a signal transduction pathway leads to regulation of one or more cellular activities
    • -these responses to stimulation involve increased activity of enzymes
    • -this can occur by transcriptional regulation or post transductional modification
  6. Transcriptional regulation
    specific transcription factors bind directly to specific regions of DNA and control transcription of genes
  7. Positive transcription factors
    proteins that increase the transcription of specific genes
  8. negative transcription factors
    proteins that decrease the transcription of specific genes
  9. Post-translational modification
    • involves modification of existing proteins in the signal response
    • -often involves the phosphorylation of specific amino acids
  10. Hormones
    chemical signals that coordinate different parts of an organism
  11. Charles Darwin and his son Francis conducted experiments on phototropism, what did they find?
    that grass seedling could bend toward light only if the tip of the coleoptile was present
  12. phototropism
    a plant's response to light
  13. Boysen- Jensen continued the phototropism experiment how?
    tip is separated by a gelatin permeable barrier or an impermeable one
  14. Auxin
    • refers to any chemical that promotes elongation of coleoptiles
    • -IAA is one common in plants
  15. Auxin transporter proteins
    move the hormone from the basal end of one cell into the apical end of the neighboring cell
  16. Role of auxin in cell elongation
    • stimulates the proton pumps in the plasma membrane
    • -proton pumps lower the pH in the cell wall
    • -expansins loosen cellulose and the cell can elongate
  17. expansins
    enzymes that loosen the cell wall's fabric
  18. auxins are used as what for lawns?
  19. auxin affects what by inducing cell division in the vascular cambium and influencing differentiation of secondary xylem
    secondary growth
  20. cytokinins
    • stimulate cytokinesis (cell division)
    • produced in actively growing tissues (roots, embryos, and fruits)
    • work with auxin to control cell division and differentiation
    • inhibit protein breakdown
  21. Gibberellins
    stimulate growth of leaves and stems
  22. Fruit growth
    both auxin and gibberellins must be present for fruit to set
  23. Germination
    after water is imbibed, release of gibberellins from the embryo signals seeds to germinate
  24. brassinoidsteriods
    • -chemically similar to the sex hormones of animals
    • - induce cell elongation and division in stem segments
  25. Acid ABA
    • -slows growth
    • seed dormancy -ensures that seed will germinate only in optimal conditions
    • -primary internal signal that enables plants to withstand drought
  26. ethylene
    • produced in response to stresses such as drought, flooding, mechanical pressure, injury, and infection
    • -effects response to mechanical stress
    • senescence
    • leaf abscission
    • fruit ripening
  27. ethylene induces the triple response which allows a growing shoot to avoid obstacles, what are the three responses
    • -slowing of stem elongation
    • -thickening of the stem
    • -horizontal growth
  28. senescence
    • programmed death of plant cells or organs
    • -a burst of ethylene is associated with apoptosis
  29. apoptosis
    the programmed destruction of cells, organs, or whole plants
  30. leaf abscission
    • a change in the balance of auxin and ethylene controls leaf abscission
    • -triggered by a burst of ethylene production (one bad apple spoils the bunch)
Card Set:
Plant Responses to Stimuli
2013-03-11 21:37:11

Life 103
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