Chapter 39 Vocabulary

Plant Response to Internal and External Stimuli

	A plant hormone that slows growth, often antagonizing actions of growth hormones. Two of its many effects are to promote seed dormancy and facilitate drought tolerance.
	A 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.
	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.
	A steroid hormone in plants that has a variety of effects, including cell elongation, retarding leaf abscission, and promoting xylem differentiation.
	A physiological cycle of about 24 hours that is present in all eukaryotic organisms and that persists even in the absence of external cues.
	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.
	A plant in which flower formation is not controlled by photoperiod or day length.
	The only gaseous plant hormone. Among its many effects are response to mechanical stress, programmed cell death, leaf abscission, and fruit ripening.
	A widespread form of plant disease resistance involving recognition of pathogen-derived molecules by the protein products of specific plant disease resistance genes.
	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.
	A response of a plant or animal to gravity.
	A protein that helps protect other proteins during heat stress. heat-shock proteins are found in plants, animals, and microorganisms.
	In multicellular organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the body to change their functioning.
	A plant's localized defense response to a pathogen, involving the death of cells around the site of infection.
	A plant that flowers (usually in late spring or early summer) only when the light period is longer than A critical length.
	A physiological response to photoperiod, the relative lengths of night and day. An example of photoperiodism is flowering.
	Growth of a plant shoot toward or away from light.
	A type of light receptor in plants that mostly absorbs red light and regulates many plant responses, such as seed germination and shade avoidance.
	The growth phase in a plant or plant part (as a leaf) from full maturity to death.
	A plant that flowers (usually in late summer, fall, or winter) only when the light period is shorter than A critical length.
	(1) In plants, a specialized plastid that contains dense starch grains and may play a role in detecting gravity. (2) In invertebrates, a grain or other dense granule that settles in response to gravity and is found in sensory organs that function in equilibrium.
	A defensive response in infected plants that helps protect healthy tissue from pathogenic invasion.
	A response in plants to chronic mechanical stimulation, resulting from increased ethylene production. An example is thickening stems in response to strong winds.
	A growth response that results in the curvature of whole plant organs toward or away from stimuli due to differential rates of cell elongation.