front 1 etiolation | back 1 Plant morphological adaptations for growing in darkness. |
front 2 de-etiolation | back 2 The changes a plant shoot undergoes in response to sunlight; also known informally as greening. |
front 3 second messengers | back 3 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. |
front 4 hormone | back 4 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, changing the target cells’ functioning. Hormones are thus important in long-distance signaling. |
front 5 tropism | back 5 A growth response that results in the curvature of whole plant organs toward or away from stimuli due to differential rates of cell elongation. |
front 6 phototropism | back 6 Growth of a plant shoot toward or away from light. |
front 7 auxin | back 7 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. |
front 8 cytokinins | back 8 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. |
front 9 gibberellins | back 9 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. |
front 10 brassinosteroids | back 10 A steroid hormone in plants that has a variety of effects, including inducing cell elongation, retarding leaf abscission, and promoting xylem differentiation. |
front 11 abscisic acid (ABA) | back 11 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. |
front 12 strigolactones | back 12 A class of plant hormone that inhibits shoot branching, triggers the germination of parasitic plant seeds, and stimulates the association of plant roots with mycorrhizal fungi. |
front 13 ethylene | back 13 A gaseous plant hormone involved in responses to mechanical stress, programmed cell death, leaf abscission, and fruit ripening. |
front 14 expansins | back 14 Plant enzyme that breaks the crosslinks (hydrogen bonds) between cellulose microfibrils and other cell wall constituents, loosening the wall’s fabric. |
front 15 apoptosis | back 15 A type of programmed cell death, which is brought about by activation of enzymes that break down many chemical components in the cell. |
front 16 triple response | back 16 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. |
front 17 senescence | back 17 The growth phase in a plant or plant part (as a leaf) from full maturity to death. |
front 18 photomorphogenesis | back 18 Effects of light on plant morphology. |
front 19 action spectrum | back 19 A graph that profiles the relative effectiveness of different wavelengths of radiation in driving a particular process. |
front 20 blue-light photoreceptors | back 20 A type of light receptor in plants that initiates a variety of responses, such as phototropism and slowing of hypocotyl elongation. |
front 21 phytochromes | back 21 A type of light receptor in plants that mostly absorbs red light and regulates many plant responses, such as seed germination and shade avoidance. |
front 22 circadian rhythyms | back 22 A physiological cycle of about 24 hours that persists even in the absence of external cues. |
front 23 photoperiodism | back 23 A physiological response to photoperiod, the relative lengths of night and day. An example of photoperiodism is flowering. |
front 24 short-day plant | back 24 A plant that flowers (usually in late summer, fall, or winter) only when the light period is shorter than a critical length. |
front 25 long-day plant | back 25 A plant that flowers (usually in late spring or early summer) only when the light period is longer than a critical length. |
front 26 day-neutral plant | back 26 A plant in which flower formation is not controlled by photoperiod or day length. |
front 27 vernalization | back 27 The use of cold treatment to induce a plant to flower. |
front 28 florigen | back 28 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. |
front 29 gravitropism | back 29 A response of a plant or animal to gravity. |
front 30 statoliths | back 30 In plants, a specialized plastid that contains dense starch grains and may play a role in detecting gravity. |
front 31 thigmomorphogenesis | back 31 A response in plants to chronic mechanical stimulation, resulting from increased ethylene production. An example is thickening stems in response to strong winds. |
front 32 thigmotropism | back 32 A directional growth of a plant in response to touch. |
front 33 action potentials | back 33 An electrical signal that propagates (travels) along the membrane of a neuron or other excitable cell as a nongraded (all-or-none) depolarization. |
front 34 abiotic | back 34 Nonliving; referring to the physical and chemical properties of an environment. |
front 35 biotic | back 35 Pertaining to the living factors—the organisms—in an environment. |
front 36 heat-shock proteins | back 36 A protein that helps protect other proteins during heat stress. Heat-shock proteins are found in plants, animals, and microorganisms. |
front 37 virulent | back 37 Describing a pathogen against which an organism has little specific defense. |
front 38 avirulent | back 38 Describing a pathogen that can mildly harm, but not kill, the host. |
front 39 gene-for-gene recognition | back 39 A widespread form of plant disease resistance involving recognition of pathogen-derived molecules by the protein products of specific plant disease resistance genes. |
front 40 hypersensitive response | back 40 A plant’s localized defense response to a pathogen, involving the death of cells around the site of infection. |
front 41 systematic acquired resistance | back 41 A defensive response in infected plants that helps protect healthy tissue from pathogenic invasion. |
front 42 salicylic acid | back 42 A signaling molecule in plants that may be partially responsible for activating systemic acquired resistance to pathogens. |
front 43 Environmental stress: Drought | back 43 Major Response: ABA production, reducing water loss by closing stomata |
front 44 Environmental stress: Flooding | back 44 Major Response: Formation of air tubes that help roots survive oxygen deprivation |
front 45 Environmental stress: Salt | back 45 Major Response: Avoiding osmotic water loss by producing solutes tolerated at high concentrations |
front 46 Environmental stress: Heat | back 46 Major Response: Synthesis of heat-shock proteins, which reduce protein denaturation at high temperatures |
front 47 Environmental stress: Cold | back 47 Major Response: Adjusting membrane fluidity; avoiding osmotic water loss; producing antifreeze proteins |