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small, nonprotein, water-soluble molecule or ion, such as calcium ion or cyclic AMP, that relays a signal to a cell's interior in response to a signal received by a signal receptor protein
one of many types of circulating chemical signals that are formed in specialized cells, travel in body fluids, and act on specific target cells to change their functioning
growth response that results in the curvature of whole plant organs toward or away from stimuli owing to differential rates of cell elongation
a class of plant hormones, including indoleacetic acid (IAA), having a variety of effects, such as phototropic response through the stimulation of cell elongation, stimulation of secondary growth, and the development of leaf traces and fruit
plant enzymes that break the crosslinks (hydrogen bonds) between cellulose microfibrils and other cell wall constituents, loosening the cell wall's fabric
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
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 stimulate fruit development with auxin
steroid hormones in plants that have a variety of effects, including cell elongation, retarding lead abscission, and promoting xylem differentiation
abscisic acid (ABA)
plant hormone that slows down growth, often antagonizing actions of growth hormones. Two of its many effects are to promote seed dormancy and facilitate drought tolerance
The only gaseous plant hormone. Among its many effects are response to mechanical stress, programmed cell death, leaf abscission, and fruit ripening.
plant growth maneuver in response to mechanical stress, involving slowing of stem elongation, a thickening of the stem, and a curvature that causes the stem to start growing horizontally
changes that occur within a cell as it undergoes programmed cell death, which is brought about by signals that trigger the activation of a cascade of suicide proteins in the cell destined to die
graph that depicts the relative effectiveness of different wavelengths of radiation in driving a particular process
class of light receptors in plants; this color light initiates a variety of responses, such as phototropism and slowing of hypocotyl elongation
physiological cycle of about 24 hours that is present in all eukaryotic organisms and that persists even in the absence of external cues
physiological response to photoperiod, the relative lengths of night and day; an example is flowering
plant that flowers (usually in late summer, fall, or winter) only when the light period is shorter than a critical length
plant that flowers (usually in late spring or early summer) only when the light period is longer than a critical length
flowering signal, not yet chemically identified, that may be a hormone or may be a change in relative concentrations of multiple hormones
a specialized plastid that contains dense starch grains and may play a role in detecting gravity
response in plants to chronic mechanical stimulation, resulting from increased ethylene production. An example is thickening stems in response to strong winds
rapid change in the membrane potential of an excitable cell, caused by stimulus-triggered, selective opening and closing of voltage-sensitive gates in sodium and potassium ion channels
widespread form of plant disease resistance involving recognition of pathogen-derived molecules by the protein products of specific plant disease resistance genes
type of elicitor (molecule that induces a broad defense response in plants) that is derived from cellulose fragments released by cell wall damage
an antibiotic, produced by plants, that destroys microorganisms or inhibits their growth
systematic acquired resistance
defensive response in infected plants that helps protect healthy tissue from pathogenic invasion
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