Chapter 39 Flashcards
One of a ribosome’s three binding sites for tRNA during translation. The E site is the place where discharged tRNAs leave the ribosome. (E stands for exit.)
E site
Effects of light on plant morphology.
photomorphogenesis
Pathogen-encoded protein that cripples the host’s innate immune system.
effector
A physiological cycle of about 24 hours that persists even in the absence of external cues.
circadian rhythm
A plant that flowers (usually in late summer, fall, or winter) only when the light period is shorter than a critical length.
short-day plant
A flowering signal, probably a protein, that is made in leaves under certain conditions and that travels to the shoot apical meristems, inducing them to switch from vegetative to reproductive growth.
florigen
Plant enzyme that breaks the cross-links (hydrogen bonds) between cellulose microfibrils and other cell wall constituents, loosening the wall’s fabric.
expansin
Any of a class of related plant hormones that retard aging and act in concert with auxin to stimulate cell division, influence the pathway of differentiation, and control apical dominance.
cytokinin
Nonliving; referring to the physical and chemical properties of an environment.
abiotic
A directional growth of a plant in response to touch.
thigmotropism
Any of a class of related plant hormones that stimulate growth in the stem and leaves, trigger the germination of seeds and breaking of bud dormancy, and (with auxin) stimulate fruit development.
gibberellin
A type of light receptor in plants that initiates a variety of responses, such as phototropism and slowing of hypocotyl elongation.
blue-light photoreceptor
A signaling molecule in plants that may be partially responsible for activating systemic acquired resistance to pathogens.
salicylic acid
A physiological response to photoperiod, the interval in a 24-hour period during which an organism is exposed to light. An example of photoperiodism is flowering.
photoperiodism
The use of cold treatment to induce a plant to flower.
vernalization
A growth response that results in the curvature of whole plant organs toward or away from stimuli due to differential rates of cell elongation.
tropism
A response in plants to chronic mechanical stimulation, resulting from increased ethylene production. An example is thickening stems in response to strong winds.
thigmomophogenesis
Short molecular sequences that typify certain groups of pathogens and that are recognized by cells of the innate immune system.
pathogen-associated molecular patterns (PAMPs)
A gaseous plant hormone involved in responses to mechanical stress, programmed cell death, leaf abscission, and fruit ripening.
ethylene
A small, nonprotein, water-soluble molecule or ion, such as a calcium ion (Ca2+) or cyclic AMP, that relays a signal to a cell’s interior in response to a signaling molecule bound by a signal receptor protein.
second messenger
The growth phase in a plant or plant part (as a leaf) from full maturity to death.
senescence
A protein that helps protect other proteins during heat stress. Heat-shock proteins are found in plants, animals, and microorganisms.
heat-shock protein
Pertaining to the living factors—the organisms—in an environment
biotic
A graph that profiles the relative effectiveness of different wavelengths of radiation in driving a particular process.
action spectrum
Any of a class of plant hormones that inhibit shoot branching, trigger the germination of parasitic plant seeds, and stimulate the association of plant roots with mycorrhizal fungi.
strigolactone
Plant morphological adaptations for growing in darkness.
etiolation
A plant growth maneuver in response to mechanical stress, involving slowing of stem elongation, thickening of the stem, and a curvature that causes the stem to start growing horizontally.
triple response
In animal behavior, a process involving transmission of, reception of, and response to signals. The term is also used in connection with other organisms, as well as individual cells of multicellular organisms.
communication
A response of a plant or animal to gravity.
gravitopism
Any of a class of plant hormones that regulate a wide range of developmental processes in plants and play a key role in plant defense against herbivores.
jasmonate
A plant that flowers (usually in late spring or early summer) only when the light period is longer than a critical length.
long-day plant
Growth of a plant shoot toward or away from light.
phototropism
The changes a plant shoot undergoes in response to sunlight; also known informally as greening.
de-etiolation
A defensive response in infected plants that helps protect healthy tissue from pathogenic invasion.
systemic acquired resistance
A plant hormone that slows growth, often antagonizing the actions of growth hormones. Two of its many effects are to promote seed dormancy and facilitate drought tolerance.
abscisic acid (ABA)
A plant in which flower formation is not controlled by photoperiod or day length.
Day-neutral plants
A steroid hormone in plants that has a variety of effects, including inducing cell elongation, retarding leaf abscission, and promoting xylem differentiation.
brassinosteroid
A plant’s localized defense response to a pathogen, involving the death of cells around the site of infection.
hypersensitive response
A type of light receptor in plants that mostly absorbs red light and regulates many plant responses, such as seed germination and shade avoidance.
phytochrome
A term that primarily refers to indoleacetic acid (IAA), a natural plant hormone that has a variety of effects, including cell elongation, root formation, secondary growth, and fruit growth.
auxin
