Biology 172

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Biology 172

• Chapter 39
• Plant Responses to Internal and External Signals

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Light and Etiolation
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Signal Transduction
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Signal Transduction and De-etiolation
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Additional Levels of Regualtion

• Transcriptional Regulation
• Positive Transcription Factors
• Negative Transcription Factors
• Post Translational Modification of Proteins
• Phosphorylation
• Second Messengers
• cGMP
• Phytochromes Protein Kinase Activation

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Discovery of Plant Hormones
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Plant Hormones

• Auxin (IAA)
• Cytokinins
• Gibberellins
• Brassinosteroids
• Abscisic Acid
• Ethylene

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Auxins

• Cell Elongation H Pumps, Expansins
• Acid Growth Hypothesis
• Lateral and Adventitious Root Formation
• Auxins As Herbicides 2,4-D
• Cell Division Vascular Cambium
• Differentiation of Secondary Xylem
• Seed Production of Auxin Fruit Development

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Cytokinins

• Cell Division
• Direct Inhibition Hypothesis
• Apical Dominance
• May Retard Aging
• RNA and Protein Synthesis
• Nutrient Relocation

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Apical Dominance
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Gibberellins

• Discovery - Gibberella
• Stem and Leaf Elongation
• Cell Division Cell Wall Loosening Enzymes
• Fruit Growth Interact with Auxin
• Seed Germination Breaking of Dormancy
• Over 100

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Gibberellins
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Gibberellins Seed Germination
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Brassinosteroids

• Chemically Similar to Cholesterol
• Cell Elongation and Division
• Stems and Seedlings
• Prevent Abscission
• Xylem Differentiation

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Abscisic Acid

• Genwrally Slows Growth
• Seed Dormancy
• ProteinnProtection
• Washing Away or Inactivation
• Lower Ratio to Gibberellins
• Drought Tolerance
• Closing of Stomata

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Abscisic Acid Seed Germination
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Ethylene

• Apoptosis
• Abscission
• Fruit Ripening
• Triple Response to Mechanical Stress
• Slows stem elongation
• Thickens stem
• Initiates horizontal Growth
• Ethylene production reduced as tip pushes
  through soil surface

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Ethylene Triple Response
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Ethylene Leaf Abscission
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Photomorphogenesis

• Effects on Plant Morphology
• Measure Days and Seasons
• Blue Light Receptors or Cryptochrome
• Cryptochromes - Inhibits Hypocotyl Elongation
• Phototropin - Phototropism
• Zeaxanthin - Light Induced Opening of Stomata
• Phytochromes
• Red/far-red receptors

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Phytochromes

• Red vs. Far-Red
• Seed Germination
• Shade Avoidance
• Higher Ratio of Far-Red to Red

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Light Receptors
Phytochromes
Blue Light Receptors
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Circadian Rhythms Sleep Movements 26 Hours
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Flowering Hormone? - Florigen
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Gravitropism
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Thigmomorphogenesis
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Thigmotropism