Plant Responses to Internal and External Signals Concept 391 Concept 391 Concept 391 Messages are sent by hormones through a signaltransduction pathway a hormone binds to a specific receptor on the cell wall ID: 465530
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Slide1
Chapter 39 Notes
Plant Responses to Internal and External SignalsSlide2
Concept 39.1Slide3
Concept 39.1Slide4
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 signalSlide5
Concept 39.1Slide6
Concept 39.1Slide7
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 responsesSlide8
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 occurSlide9
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 coleoptileSlide10
Concept 39.2Slide11
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 Slide12
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 growthSlide13
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 growSlide14
Concept 39.2Slide15
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
Slide16
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 Slide17
Concept 39.2Slide18
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 dwarfedSlide19
Concept 39.2Slide20
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 Slide21
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 obstacleSlide22
Concept 39.2Slide23
Concept 39.2