Chapter 39: Plant Responses to Internal and External Signals Jay Swan Cincinnati, Ohio.
Chapter 39 Notes Plant Responses to Internal and External Signals.
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Transcript of Chapter 39 Notes Plant Responses to Internal and External Signals.
![Page 1: Chapter 39 Notes Plant Responses to Internal and External Signals.](https://reader035.fdocuments.us/reader035/viewer/2022062301/5697bfc31a28abf838ca55c3/html5/thumbnails/1.jpg)
Chapter 39 Notes
Plant Responses to Internal and External
Signals
![Page 2: Chapter 39 Notes Plant Responses to Internal and External Signals.](https://reader035.fdocuments.us/reader035/viewer/2022062301/5697bfc31a28abf838ca55c3/html5/thumbnails/2.jpg)
Concept 39.1
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Concept 39.1
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Concept 39.1
Messages are sent by hormones through a signal-transduction pathway- a hormone binds to a specific receptor on the cell wall- the binding stimulates the production of a secondary messenger- the secondary messenger trigger's the cell’s response to the original signal
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Concept 39.1
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Concept 39.1
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Concept 39.2
Hormones: chemical signals that coordinate the parts of an organism- compound that is produced by one part of the body and is transported to other parts to bind to receptors in order to trigger responses
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Concept 39.2
Tropism: any growth response that results in curvatures of whole plant organs toward or away from stimuli
Phototropism: the growth of a shoot toward light- directs growing seedlings so photosynthesis can occur
![Page 9: Chapter 39 Notes Plant Responses to Internal and External Signals.](https://reader035.fdocuments.us/reader035/viewer/2022062301/5697bfc31a28abf838ca55c3/html5/thumbnails/9.jpg)
Concept 39.2
- the tip of the seeding is enclosed in a sheath called the coleoptile; if the tip is removed, the coleoptile would not curve- a signal is transmitted downward from the tip of the elongating region of the coleoptile
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Concept 39.2
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Concept 39.2
Plant hormones help coordinate growth, development, and responses to environmental stimuli- response to a hormone depends on its relative concentration compared with other hormones- hormonal balance controls growth and development
![Page 12: Chapter 39 Notes Plant Responses to Internal and External Signals.](https://reader035.fdocuments.us/reader035/viewer/2022062301/5697bfc31a28abf838ca55c3/html5/thumbnails/12.jpg)
Concept 39.2
Auxin- any chemical substance that promotes the elongation of coleoptiles- moves from the shoot tip down to the base of the plant- if concentrations are too high, auxin will inhibit growth
![Page 13: Chapter 39 Notes Plant Responses to Internal and External Signals.](https://reader035.fdocuments.us/reader035/viewer/2022062301/5697bfc31a28abf838ca55c3/html5/thumbnails/13.jpg)
Concept 39.2
- auxin stimulates proton pumps which in turn increases voltage across the membrane and lowers the pH in the cell wall- the acidification activates enzymes called expansins which help allow the cell to grow
![Page 14: Chapter 39 Notes Plant Responses to Internal and External Signals.](https://reader035.fdocuments.us/reader035/viewer/2022062301/5697bfc31a28abf838ca55c3/html5/thumbnails/14.jpg)
Concept 39.2
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Concept 39.2
Cytokinins- stimulate cytokinesis, or cell division- produced in actively growing tissues; are needed to be present along with auxin for cells to divide
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Concept 39.2
Cytokinins and auxin control apical dominance, the ability of the terminal bud to suppress the development of axillary buds- if the terminal bud is removed, the inhibition of axillary buds is removed and the plant becomes bushier
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Concept 39.2
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Concept 39.2
Gibberellins- stimulate growth in the stems and leaves, but not in the roots- stimulates cell elongation and division- the effects of gibberellins are seen when they are given to a plant that is dwarfed
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Concept 39.2
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Concept 39.2
Abscisic Acid- slows down growth- seed dormancy: high levels of ABA inhibit germination; only when the ABA is inactivated will the seed germinate- drought stress: when a plant begins to wilt, ABA causes stomata to close
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Concept 39.2
Ethylene- produced by plants in response to environmental stresses- also occurs in fruit ripening and programmed cell death- triple response that allows plants to circumvent an obstacle
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Concept 39.2
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Concept 39.2