Chapter 39: Plant Responses to Internal and External Signals Flashcards
Leaf Abscission
when a plant drops its leaves
cytokinin
plant hormones that influence growth and the stimulation of cell division (can slow aging of plant organs)
Auxin
a plant hormone which causes the elongation of cells in shoots and is involved in regulating plant growth
ethylene
plants produce this in response to stresses such as
drought, flooding, mechanical pressure, injury, and infection
xanthophylls
class of oxygen-containing carotenoid pigments (cause orange pigment)
Plants sense a diverse array of
stimuli including:
Light Gravity Touch, wind Drought, floods Temperature Heavy metals Herbivores, pathogens
Photomorphogenesis
development of form and structure in plants which is affected by light, other than that occurring for photosynthesis
Gravitropism
important plant growth response to the environment that directs shoots upward and roots downward
Thigmotropism
the turning or bending of a plant or other organism in response to a touch stimulus
Thigmomorphogenesis
the response by plants to mechanical sensation (touch) by altering their growth patterns
Response to drought
Abscisic acid (ABA) production, reducing water loss by closing stomata
Response to flooding
Formation of air tubes that help roots survive oxygen deprivation; stimulates ethylene
Response to salt
Avoiding osmotic water loss by producing solutes tolerated at high concentrations
Response to heat
Synthesis of heat-shock proteins, which reduce protein denaturation at high temperatures
Response to cold
Adjusting membrane fluidity; avoiding osmotic water loss; producing antifreeze proteins
Plants counter herbivory with…
physical defenses, such as thorns and trichomes, and chemical defenses, such as distasteful or toxic compounds
hypersensitive response
a form of cell death often associated with plant resistance to pathogen infection
systemic acquired resistance
a plant defense response that provides long-lasting, broad-spectrum pathogen resistance to uninfected systemic leaves following an initial localized infection
signal transduction pathway
a mechanism linking a mechanical or chemical stimulus to a specific cellular response
Transcriptional regulation
end products of signal transduction pathway increase or decrease the rate of transcription of specific genes
Post-translational modification
end products of signal transduction pathway modify existing proteins to make them more or less active
Two major classes of light receptors:
blue-light photoreceptors (detect/respond to blue light) and phytochromes (detect/respond to red and far red light)
Chlorophyll absorbs ____ and ____ wavelengths
red, blue
Seed germination occurs during ____ illumination
red light
phytochrome system
provides the plant with information about the quality of light
Photoperiod
relative lengths of night and day
Photoperiodism
a physiological response to photoperiod
Short-day plants
governed by minimum number of hours of darkness
Long-day plants
governed by maximum number of hours of darkness
Day-neutral plants
flowering is controlled by plant maturity
It is the length of ______ that plays the most crucial role in flowering
darkness
De-etiolation
“greening”
Etiolation
plant morphological adaptations for growing in the darkness
tropism
response of a plant organ toward or away from a stimulus
acid growth hypothesis
auxin stimulates proton pumps in the plasma membrane & loosens cellulose
Gibberellins
stimulate growth of leaves and stems
Abscisic acid (ABA)
slows growth by antagonizing the actions of the growth hormones—auxins, cytokinins, and gibberellins
Two effects of ABA
Seed dormancy
Drought signaling
