Download Chapter 39 Presentation

Chapter 39
Plant Responses to Internal
and External Signals
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 39-2
Concept 39.1: Signal transduction pathways link
signal reception to response
(a) Before exposure to light
(b) After a week’s exposure to
natural daylight
Fig. 39-4-1
1
Reception
2
Transduction
CYTOPLASM
Plasma
membrane
cGMP
Second messenger
produced
Phytochrome
activated
by light
Cell
wall
Light
Specific
protein
kinase 1
activated
NUCLEUS
Fig. 39-4-2
1
Reception
2
Transduction
CYTOPLASM
Plasma
membrane
cGMP
Second messenger
produced
Specific
protein
kinase 1
activated
Phytochrome
activated
by light
Cell
wall
Specific
protein
kinase 2
activated
Light
Ca2+ channel
opened
Ca2+
NUCLEUS
Fig. 39-4-3
1
Reception
2
Transduction
3
Response
Transcription
factor 1
CYTOPLASM
Plasma
membrane
cGMP
Second messenger
produced
Specific
protein
kinase 1
activated
NUCLEUS
P
Transcription
factor 2
Phytochrome
activated
by light
P
Cell
wall
Specific
protein
kinase 2
activated
Transcription
Light
Translation
Ca2+ channel
opened
Ca2+
De-etiolation
(greening)
response
proteins
Concept 39.2: Plant hormones help coordinate
growth, development, and responses to stimuli
• _______________are chemical signals that
coordinate different parts of an organism
• Any response resulting in curvature of organs
toward or away from a stimulus is called a
_______________
• Tropisms are often caused by hormones
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A Survey of Plant Hormones
• In general, hormones control plant growth and
development by affecting the division,
elongation, and differentiation of cells
• Plant hormones are produced in very low
concentration, but a minute amount can greatly
affect growth and development of a plant organ
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Table 39-1
Auxin
• Stimulates stem elongation and growth by
softening cell wall
• ___________________
– Growth towards light
– Asymmetrical distribution of auxin (cells on
darker side elongate faster than cells on
brighter side)
• Enhances ____________________, so plants
grow upwards rather than laterally
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Cytokinins
• Stimulate _______________(cell division)
• Work together with ________ to control cell
division and differentiation
• Produced in ______ and travel upwards
• Delay _____________ (aging of plant organs)
by inhibiting protein breakdown, stimulating
RNA and protein synthesis, and mobilizing
nutrients from surrounding tissues
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Gibberellins
• Family of hormones
– over 100 different gibberellins identified
• Effects
– ____________________
– ____________________
– ____________________
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plump grapes in grocery
stores have been treated
with gibberellin hormones
while on the vine
Brassinosteroids
• Brassinosteroids are chemically similar to the
sex hormones of animals
• They induce cell elongation and division in
stem segments
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Abscisic Acid
• Abscisic acid (ABA) slows growth
• Two of the many effects of ABA:
___________________
___________________
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Ethylene
• Ethylene is a ________
• Plants produce ethylene in response to
stresses such as drought, flooding, mechanical
pressure, injury, and infection
• Effects include:
– ____________________
– ____________________
– ____________________
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Fruit ripening
• Adaptation
– hard, tart fruit protects
developing seed from herbivores
– ripe, sweet, soft fruit attracts
animals to disperse seed
• Mechanism
– triggers ripening process
• breakdown of cell wall
– softening
• conversion of starch to sugar
– sweetening
– positive feedback system
• ethylene triggers ripening
• ripening stimulates more ethylene
production
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 39-15
0.5 mm
Protective layer
Stem
Abscission layer
Petiole
Concept 39.3: Responses to light are critical for
plant success
• Light cues many key events in plant growth
and development
• There are two major classes of light receptors:
____________________
and
____________________
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Fig. 39-UN1
Red light
Pr
Pfr
Far-red light
Biological Clocks and Circadian Rhythms
• Many plant processes oscillate during the day
• _____________________ are cycles that are
about 24 hours long and are governed by an
internal “clock”
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Photoperiodism and Responses to Seasons
• Photoperiod, the relative lengths of night and
day, is the environmental stimulus plants use
most often to detect the time of year
• Photoperiodism is a physiological response to
photoperiod
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Photoperiodism and Control of Flowering
• Some processes, including flowering in many
species, require a certain photoperiod
• Plants that flower when a light period is shorter
than a critical length are called
________________________
• Plants that flower when a light period is longer
than a certain number of hours are called
________________________
• Flowering in day-neutral plants is controlled
by plant maturity, not photoperiod
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 39-21
24 hours
(a) Short-day (long-night)
plant
Light
Critical
dark period
Flash
of
light
Darkness
(b) Long-day (short-night)
plant
Flash
of
light
You should now be able to:
1. Compare the growth of a plant in darkness
(etiolation) to the characteristics of greening
(de-etiolation)
2. List six classes of plant hormones and
describe their major functions
3. Describe the phenomenon of phytochrome
photoreversibility and explain its role in lightinduced germination of lettuce seeds
4. Explain how light entrains biological clocks
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
5. Distinguish between short-day, long-day, and
day-neutral plants; explain why the names are
misleading
6. Describe how plants tell up from down
7. Distinguish between thigmotropism and
thigmomorphogenesis
8. Describe the challenges posed by, and the
responses of plants to, drought, flooding, salt
stress, heat stress, and cold stress
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
9. Describe how the hypersensitive response
helps a plant limit damage from a pathogen
attack
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings