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7 Cards in this Set
- Front
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Regulate Growth |
4 Types 1) Environmental Factors 2) Receptors 3) Hormones 4) Genes |
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Environmental Factors |
- Tropisms: directional response to directional stimulus - Phototropism: growth or movement of plant towards light - Gravitropism: growth of plant towards gravity - Thigmotropism: growth of plant in response to touch |
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Detect light |
- most important response - tip of outer sheath of seedling (coleoptile) detects light - Action spectrum: only sensitive to blue light - have molecule that changes shape when exposed to particular wavelength - Blue Light: phototropin - movement, stomata - Red Light: phytochrome - germination, elongation |
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Plant Receptor |
1) Stimulus: light, pressure, touch, temp 2) Hormone released: stimulus converted to intracellular signal 3) Signal cascade: hormone binds to receptor 4) Response to stimuli: change in transcription, translation, ion flow, enzyme activation |
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Plant Hormone |
AUXIN: Stem elongation |
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Auxin |
- regulate phototropism & gravitropism - Auxin transport is polar (unidirectional) 1) Diffusion across plasma membrane - auxin released from coleoptiles - diffuse to adjacent cell then through cytosol 2) Membrane protein asymmetry - asymmetric distribution of auxin transporters keep moving in unidirection 3) Proton pumping/electrochemical gradient - ATP proton pump removes H+ from cell 4) Ionization of weak acid - low pH in cell wall drives equation to right EXPOSED TO DIRECT LIGHT, MOVES TO SIDE OF CELL |
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Acid Growth Hypothesis |
- Auxin has two effects 1) Change in gene expression - auxin stimulates synthesis of more pumps - more pumps=lower pH=further activation of expansin 2) Enzymatic Action - to expand, cell wall must be "loosened" - auxin guides more proton pumps into plasma membrane = lower pH in wall - lower pH activates expansin = loosen wall |
