Ch. 39 B Flashcards
What are the effects of gibberellins (5)
1) Stem Elongation
2) Fruit Growth
3) Seed Germination
4) Flowering
5) Leaf Expansion
How do Gibberellins stimulate growth?
Enhancing cell division and elongation
Where are Gibberellins produced?
Young roots and shoots
What is bolting?
Rapid growth of floral stalk
What is required for fruit development?
Auxin and Gibberellin
What does the release of gibberellins indicate to the embryo?
The germination of the seed (after imbibition)
What is the function of Amylase?
Breaks down amylose
What does Abscisic acid do? What does it affect?
1) It slows growth by stopping the actions of growth hormones
2) Causes seed dormancy and drought tolerance
What does the ratio of ABA to gibberellins indicate?
Affects whether the seeds will break dormancy
What causes early germination?
Low levels of ABA
What is the primary signal that enables plants to withstand a drought
ABA
ABA accumulation causes what for drought tolerance
Stomata to close rapidly (wilting of leaves)
What does the transport of ABA from water-stressed root system to leaves indicate?
Early warning system
Abiotic Stress (Plant Development)
Primary Metabolites
Heat, cold, drought, salt, metals, flooding
Biotic Stress (Plant Defense)
Phytohormones
Herbivore attack, Insect attack, Pathogen attack
When do plants produce ethylene?
Response to stress: Drought, flooding, mechanical pressure, injury and infection
What are the effects of ethylene? (3)
Senescence: Loss of cell division and growth
Leaf abscission: less leaves
Fruit Ripening
What is the triple response to mechanical stress?
1) Triple response: Elongation slowed, thickened stem, and horizontal stem growth
2) Happens when seedling tips is pressed against obstacle ethylene is produced
3) Absence of ethylene causes normal growth
What is senescence? When does it happen?
Programmed death of certain cells or organs or entire plant
Burst of ethylene is associated with apoptosis
What is Leaf Abscission?
Change in balance of auxin and ethylene causes leaves to fall and DIE
What triggers ripening?
Release of more ethylene
Change in shape due to a response to light
Photomorphogenesis
What can plants detect?
Light: presence, direction, intensity, and color
Two major classes of light receptors?
1) Blue light photoreceptors
2) Phytochromes
What does blue light initiate?
1) Hypocotyl elongation
2) Stomatal opening
3) phototropism
What is phototropin?
Protein kinase involved in mediating plant responses to blue light
What do phytochromes do? (3)
Pigments that regulate plant response to light
De-etiolation, seed germination (red light), and shade avoidance
What does red light cause
Induced germination
What inhibits germination?
Far-red light
Are the effects of red and far-red light reversible?
Yes
What does final light exposure do?
Determines the response (for seed germination)
What are the two photoreversible states
Pr and PFr
What triggers the conversion of Pr to Pfr
Red light (faster than the reverse reaction)
What triggers the conversion of PFr to Pr
Far-red light
What contains both red and far red light thus causing germination?
Sunlight
Red light nm?
600-700
Far red light nm?
700-750
Explain the interaction of canopy leaves and red and far-red light
they absorb red light and allow far-red light to pass through to shaded leaves
what does Pr induce?
vertical growth
plant processes and circadian rhythms
1) some processes affected by light and temperature
2) others under frequency of 24 hr even under constant conditions
photoperiod
lengths of night and day
environmental stimulus to detect time of year
Photoperiodism
physiological response to photoperiod
Short-day plants
light period is shorter than a critical length
governed by minimum hours of consecutive darkness
(if maximum consecutive darkness is exceeded= flowering)
Long-day plants
light period longer than a certain number of hours
governed by maximum hours of darkness
(if maximum consecutive darkness is exceeded= no flowering)
Day-neutral plants
controlled by plant maturity not photoperiod
photoperiods are controlled by what?
critical night length
gravitropism
response to gravity
How are roots and shoots affected by gravitropism?
roots show positive
shoots show negative
what are statoliths?
cytoplasmic components that help plants detect gravity
Thigmomorphogenesis
changes in form from mechanical disturbance
ex) rubbing stems
Thigmotropism
growth in response to touch
what are Action potentials?
touch response from electrical impulses
How do plants reduce transpiration? (3)
1) closing stomata
2) reducing exposed surface area
3) shedding leaves
How do plants survive flooding?
1) enzymatic destruction of root cortex
2) aerial roots
How do plants respond to salt stress?
producing solutes that tolerate high concentration
How do plants respond to heat stress? (2)
1) transpiration
2) heat-shock proteins
How do plants respond to cold stress? (3)
1) alter lipid composition in membranes
2) increase solute concentration in cytosol to reduce water loss
3) antifreeze proteins
describe plant response to attacks by pathogens and herbivores
use defense systems
